Idioms are fun phrases where the words together have a special meaning that is different from their actual words. People use idioms to make their speaking and writing more colorful, playful, and interesting. In this guide, you will learn many popular idioms used to describe a crazy person or someone acting very silly.
In this lesson, we will look at idioms that mean someone is acting wild, strange, or out of their mind. Let us get started and explore some of these helpful expressions.
Idioms for Crazy Person
1. Lose one’s marbles
Definition: To act foolish, strange, or as if you have lost your mind.
Used in a Sentence: My uncle began talking to the garden wall, making everyone think he had lost his marbles. / After looking for his keys for an hour, Sam felt like he was losing his marbles.
Similar Expressions: Go crazy / Lose one’s mind
2. Off one’s rocker
Definition: Behaving in a completely silly, wild, or unreasonable way.
Used in a Sentence: You must be off your rocker if you think we can swim in this freezing water. / The old inventor was off his rocker when he tried to build a flying bicycle.
Similar Expressions: Out of your head / Not in one’s right mind
3. A screw loose
Definition: Having strange thoughts or behaving in a slightly crazy manner.
Used in a Sentence: That guy yelling at the pigeons surely has a screw loose. / My brother says I have a screw loose because I like eating peanut butter with pickles.
Similar Expressions: Not all there / A bit cracked
4. Out of one’s mind
Definition: Acting very wild, dangerous, or completely irrational.
Used in a Sentence: Are you out of your mind jumping on the bed right after dinner? / The dog went out of its mind with excitement when mom opened the treat box.
Similar Expressions: Beside oneself / Stark raving mad
5. Go bananas
Definition: To become extremely silly, excited, or wildly angry.
Used in a Sentence: The children will go bananas if they do not get to play outside today. / The crowd went bananas when our school team scored the final goal.
Similar Expressions: Go wild / Flip out
6. Batty as a fruitcake
Definition: Being very silly, odd, or mentally eccentric.
Used in a Sentence: Grandfather is batty as a fruitcake when he starts dancing in the kitchen without music. / People thought the artist was batty as a fruitcake for painting his entire house pink.
Similar Expressions: Nutty as a fruitcake / Wacky
7. Bats in the belfry
Definition: Having strange, eccentric, or crazy thoughts inside your head.
Used in a Sentence: Anyone who wants to hike up a snowy mountain in shorts must have bats in the belfry. / The pirate had bats in the belfry after spending years searching for magical islands.
Similar Expressions: Crazy thoughts / Head full of nonsense
8. Mad as a hatter
Definition: Completely wild, silly, or acting crazy.
Used in a Sentence: The scientist looked mad as a hatter with his hair sticking straight up in the air. / She was mad as a hatter to trade her brand new bicycle for an old comic book.
Similar Expressions: Completely nuts / Out of one’s wits
9. Out of one’s tree
Definition: Acting very odd, foolish, or irrational.
Used in a Sentence: He is out of his tree if he thinks he can finish the whole pizza alone. / Mom thought Dad was out of his tree when he bought a giant inflatable dinosaur.
Similar Expressions: Off your head / Cuckoo
10. Not the sharpest tool in the shed
Definition: Acting silly or lacking basic common sense.
Used in a Sentence: Leaving the chocolate bar out in the hot sun proved he was not the sharpest tool in the shed. / He tried to cut soup with a fork and showed he was not the sharpest tool in the shed.
Similar Expressions: A bit dim / Not very bright
11. Go bonkers
Definition: To become totally wild, hyperactive, or crazy.
Used in a Sentence: The puppies go bonkers whenever the doorbell rings. / I will go bonkers if I have to listen to that squeaky door all afternoon.
Similar Expressions: Go nuts / Go haywire
12. Drive someone up the wall
Definition: To make another person feel so annoyed that they feel crazy.
Used in a Sentence: That loud ticking clock is driving me up the wall while I try to sleep. / The baby crying on the long bus ride drove the passengers up the wall.
Similar Expressions: Drive someone crazy / Make one lose one’s mind
13. Not playing with a full deck
Definition: Lacking good sense or acting mentally confused.
Used in a Sentence: Thinking you can fly using an umbrella means you are not playing with a full deck. / The neighbor is not playing with a full deck since he washes his car while it is raining.
Similar Expressions: Missing a few cards / Short of a full load
14. Off the deep end
Definition: To react in an extreme, unreasonable, or crazy way.
Used in a Sentence: Dad went off the deep end when he saw the muddy footprints on the white carpet. / She went off the deep end after losing her video game match.
Similar Expressions: Overreact wildly / Lose all control
15. A few sandwiches short of a picnic
Definition: Missing common sense or acting in an eccentric, foolish way.
Used in a Sentence: He wore winter boots to the beach and looked a few sandwiches short of a picnic. / The boy who tried to open a window on an airplane seemed a few sandwiches short of a picnic.
Similar Expressions: A brick short of a load / Not fully sensible
16. Out to lunch
Definition: Being completely daydreamy, crazy, or disconnected from reality.
Used in a Sentence: The teacher called his name three times because he was totally out to lunch. / Anyone who believes the moon is made of cheddar cheese is out to lunch.
Similar Expressions: In a daze / Space cadet
17. Head in the clouds
Definition: Having strange, unrealistic thoughts instead of paying attention to real life.
Used in a Sentence: Emma walked straight into the screen door because her head was in the clouds. / You cannot get any homework done with your head in the clouds all afternoon.
Similar Expressions: Daydreaming / Living in a fantasy
18. Lose one’s grip
Definition: To lose control of your mind, emotions, or sensible thinking.
Used in a Sentence: The tired student felt like he was losing his grip after studying all night. / The captain lost his grip on reality during the huge ocean storm.
Similar Expressions: Slip away / Lose mental control
19. Around the bend
Definition: Becoming crazy, senseless, or emotionally unstable.
Used in a Sentence: Staying inside during the heavy rainstorm for four days made everyone go around the bend. / The noisy construction outside is driving the workers around the bend.
Similar Expressions: Crazy as can be / Out of one’s senses
20. Touch of madness
Definition: A small amount of crazy, strange, or unpredictable behavior.
Used in a Sentence: The painter had a touch of madness that made his artwork exciting. / Choosing to run a marathon in silly costumes requires a touch of madness.
Similar Expressions: Bit of eccentricity / Wild streak
21. Go postal
Definition: To become suddenly and uncontrollably angry or wild.
Used in a Sentence: The customer went postal when the store clerk refused to give a refund. / Please stay calm and do not go postal over a simple spelling mistake.
Similar Expressions: Explode with rage / Fly into a fury
22. Not right in the head
Definition: Thinking or acting in a very bizarre, abnormal way.
Used in a Sentence: Anyone who pours hot sauce into their morning cereal is not right in the head. / That strange man talking to telephone poles is clearly not right in the head.
Similar Expressions: Mentally odd / Out of balance
23. Flip one’s lid
Definition: To suddenly become extremely angry or act completely crazy.
Used in a Sentence: Mom will flip her lid if she sees the broken flower vase on the floor. / The coach flipped his lid when the referee made an unfair call.
Similar Expressions: Blow one’s top / Lose one’s temper
24. Go off the rails
Definition: To start behaving in a completely wild, messy, or crazy way.
Used in a Sentence: The birthday party went off the rails when food started flying across the room. / The young actor went off the rails after becoming famous too quickly.
Similar Expressions: Lose direction / Spiral out of control
25. Like a headless chicken
Definition: Moving around in a panicked, disorganized, and crazy manner.
Used in a Sentence: Running like a headless chicken will not help you find your lost backpack. / The workers rushed around like headless chickens trying to finish before the deadline.
Similar Expressions: In a wild frenzy / Running all over
26. Barking mad
Definition: Completely, undeniable, and loudly crazy.
Used in a Sentence: You must be barking mad to ride your skateboard down that steep rocky hill. / The idea to build a treehouse with no ladder is barking mad.
Similar Expressions: Utterly insane / Raving mad
27. Gone off the deep end
Definition: Having completely lost touch with normal behavior or reasonable thought.
Used in a Sentence: He has gone off the deep end with his wild theories about aliens living in the garden. / Ever since she bought fifty cats, her friends say she has gone off the deep end.
Similar Expressions: Fallen into madness / Gone completely wild
28. Cuckoo in the head
Definition: Being silly, foolish, or mentally unusual.
Used in a Sentence: The parrot was cuckoo in the head and loved to sing loudly at midnight. / My little sister is a bit cuckoo in the head when she pretends to be a pirate.
Similar Expressions: Silly minded / Goofy
29. Out of one’s wits
Definition: So surprised, scared, or overwhelmed that you cannot think straight.
Used in a Sentence: The loud thunderstorm frightened the kitten out of its wits. / I was scared out of my wits when the spooky owl landed near my window.
Similar Expressions: Terrified / In a total panic
30. Blow a gasket
Definition: To explode with crazy anger and wild emotion.
Used in a Sentence: The driver blew a gasket when another car bumped into his shiny bumper. / Dad will blow a gasket if we do not finish cleaning our bedroom today.
Similar Expressions: Have a fit / Pop a fuse
31. Out of one’s gourd
Definition: Acting totally foolish, wild, or completely crazy.
Used in a Sentence: He is out of his gourd if he plans to jump into that muddy swamp. / The dog ran around the yard out of its gourd trying to catch a butterfly.
Similar Expressions: Out of your skull / Mindless
32. Lost one’s senses
Definition: Unable to think, judge, or act in a normal, logical way.
Used in a Sentence: Have you lost your senses by leaving all the front windows wide open in a storm? / The king lost his senses and ordered everyone to walk backwards on Tuesdays.
Similar Expressions: Gone irrational / Forgotten all reason
33. Pop one’s cork
Definition: To lose control of your feelings and behave in a wild rage.
Used in a Sentence: The teacher popped her cork when the entire classroom started throwing paper airplanes. / Take a deep breath so you do not pop your cork over small problems.
Similar Expressions: Lose one’s cool / Fly off the handle
34. Off the reservation
Definition: Acting outside the normal rules or in an unpredictable, rebellious way.
Used in a Sentence: The team captain went off the reservation and ignored the coach’s plan. / The scientist went off the reservation to conduct dangerous experiments in his basement.
Similar Expressions: Gone rogue / Breaking all rules
35. Have a loose cannon
Definition: A person who is wild, unpredictable, and likely to cause chaos.
Used in a Sentence: Our clumsy goalie was a loose cannon on the soccer field today. / Nobody wanted to work with the loose cannon who kept changing the project ideas.
Similar Expressions: Wild card / Unpredictable person
36. Go haywire
Definition: To suddenly become disorganized, chaotic, or wildly out of control.
Used in a Sentence: My computer went haywire and opened fifty windows all at once. / The whole plan went haywire when it started pouring rain during the parade.
Similar Expressions: Go crazy / Malfunction completely
37. As mad as a March hare
Definition: Behaving in an exceptionally wild, hyper, or strange manner.
Used in a Sentence: During spring break, the kids were as mad as a March hare in the backyard. / The puppy ran in circles looking as mad as a March hare.
Similar Expressions: Wildly excited / Full of crazy energy
38. Off the wall
Definition: Very unusual, bizarre, or unexpectedly crazy.
Used in a Sentence: His funny comedy show was completely off the wall and made everyone laugh. / She had an off the wall idea to paint our bicycles with glowing green stripes.
Similar Expressions: Highly eccentric / Wacky and strange
39. Beside oneself
Definition: Overcome with extreme emotion such as wild worry, anger, or joy.
Used in a Sentence: Mother was beside herself when the little dog slipped out of the garden gate. / The boy was beside himself with happiness when he won the grand prize.
Similar Expressions: Overcome with emotion / Frantic
40. Out of whack
Definition: Not working properly, unbalanced, or behaving strangely.
Used in a Sentence: My sleep schedule is completely out of whack after traveling across time zones. / The lawnmower engine sounded strange and totally out of whack.
Similar Expressions: Out of order / Off balance
41. Not in one’s right mind
Definition: Thinking or acting in a way that is abnormal and unreasonable.
Used in a Sentence: No one in their right mind would walk outside during a tornado warning. / She was not in her right mind when she threw away her favorite jacket.
Similar Expressions: Lacking good sense / Mentally clouded
42. Drive someone crazy
Definition: To make someone feel utterly annoyed, frustrated, or wild.
Used in a Sentence: The sound of water dripping from the bathroom sink is driving me crazy. / Having too many chores to finish in one day can drive anyone crazy.
Similar Expressions: Drive someone nuts / Make someone frantic
43. Clean off one’s trolley
Definition: Completely crazy, foolish, or out of one’s proper senses.
Used in a Sentence: You must be clean off your trolley to ride a unicycle across a rope. / The old sailor was clean off his trolley telling stories about giant sea monsters.
Similar Expressions: Completely daft / Out of your mind
44. Gone nutty
Definition: To start behaving in a very odd, silly, or wild manner.
Used in a Sentence: Everyone has gone nutty trying to buy the newest toy before the holidays. / The kittens have gone nutty chasing the red laser dot on the carpet.
Similar Expressions: Turned wacky / Gone goofy
45. Lose one’s cool
Definition: To lose calm control of yourself and become wild or upset.
Used in a Sentence: The chess player lost his cool after making a bad move on the board. / Take three deep breaths so you do not lose your cool during the test.
Similar Expressions: Lose one’s temper / Get upset
46. A brick short of a load
Definition: Someone who is lacking intelligence, good judgment, or common sense.
Used in a Sentence: Trying to microwave a metal fork shows that he is a brick short of a load. / The goofy thief was a brick short of a load and left his wallet at the scene.
Similar Expressions: Short of brains / Missing some pieces
47. Flying off the handle
Definition: Suddenly showing a massive, unexpected burst of crazy anger.
Used in a Sentence: Dad is famous for flying off the handle when he steps on a toy block. / There is no reason for flying off the handle over spilled milk on the table.
Similar Expressions: Losing control / Exploding in anger
48. Crack up
Definition: To suffer a mental breakdown or to laugh in a wild, uncontrollable way.
Used in a Sentence: The funny clown made the entire audience crack up with laughter. / The stressed manager felt like he might crack up from working twelve hours a day.
Similar Expressions: Break down / Burst out laughing
49. In a daze
Definition: Feeling confused, unable to think clearly, or acting dreamily disconnected.
Used in a Sentence: After waking up from the loud alarm, Leo walked around in a daze. / She wandered the school hallway in a daze after receiving the surprising news.
Similar Expressions: Half asleep / Mentally stunned
50. Wild as a buck
Definition: Full of uncontrollable, energetic, and unpredictable behavior.
Used in a Sentence: The young horse was wild as a buck and refused to wear a saddle. / Those boys running in the muddy park are as wild as a buck today.
Similar Expressions: Totally untamed / Full of wild energy
Exercise to Practice
- When Maria started conversing with her bedroom lamp, her sister thought she had lost her marbles.
- If you wear three heavy winter coats to the hot summer beach, you are acting off your rocker.
- Tommy used a ruler to measure his desk correctly, showing he had a screw loose.
- Jumping across the dangerous train tracks proved the brave boy was completely out of his mind.
- The children will go bananas with calm silence while they read their library books.
- Putting orange juice on your morning pancakes makes you seem batty as a fruitcake.
- The wise old professor had bats in the belfry because he solved the math problem perfectly.
- The pirate was mad as a hatter when he tried to sail a wooden boat with no bottom.
- You are out of your tree if you think you can lift a giant school bus with one finger.
- Studying hard and scoring an A on the science test proves you are not the sharpest tool in the shed.
- The excited puppies go bonkers whenever their owner comes home with a new toy.
- Listening to quiet, peaceful birds singing outside is driving me up the wall with anger.
- Trying to water the plants while wearing a bucket on your head shows you are not playing with a full deck.
- Dad went off the deep end and calmly poured a cup of warm tea for his friend.
- He packed an umbrella for a rainy day, which showed he was a few sandwiches short of a picnic.
Answer Key
- True
- True
- False
- True
- False
- True
- False
- True
- True
- False
- True
- False
- True
- False
- False
Conclusion
Learning these idioms helps you understand colorful expressions that native speakers use every day to describe unusual behavior. They give you fun, creative ways to express yourself instead of repeating basic descriptive words over and over.
Try sharing a few of these silly phrases with your friends, family, or classmates during your next conversation. Practicing idioms in your daily reading and speaking will make your English sound more natural and exciting.
Frequently Asked Questions
What does it mean when an idiom describes someone as crazy?
These idioms usually mean a person is acting silly, making foolish choices, or behaving in an unusually wild way. They are mostly playful expressions used in casual everyday conversations rather than medical descriptions.
What are some common idioms for crazy person?
Some of the most popular phrases include “lose one’s marbles,” “off one’s rocker,” and “go bananas.” Native English speakers use these lively idioms often in books, movies, and family chats.
Why do English speakers use idioms instead of plain words?
Idioms add humor, emotion, and vivid imagery to our conversations. Using a funny phrase makes stories more memorable and engaging for the person listening to you.
Are idioms for a crazy person considered polite to use?
Most of these idioms are informal and humorous, making them great for friendly chats with buddies. However, you should avoid using them in very formal settings or when talking about serious health topics.
How can I remember all these idioms easily?
The best way to remember them is by practicing a few each day in your own sentences. You can also look for them while watching English cartoons, reading storybooks, or writing funny stories.
