50 Idioms for Crazy With Meanings & Sentences
Idioms for Crazy
1. Mad as a Hatter
Meaning: Extremely crazy or eccentric.
In a Sentence: When Tim started talking to his imaginary friend, his friends thought he was mad as a hatter.
Other Ways to Say: As crazy as a loon, nutty as a fruitcake.
2. Barking Mad
Meaning: Extremely crazy or irrational.
In a Sentence: His idea to build a rollercoaster in his backyard was barking mad.
Other Ways to Say: Mad as a March hare, off the deep end.
3. Off Your Rocker
Meaning: Mentally unstable or acting irrationally.
In a Sentence: You must be off your rocker to go skydiving in a storm.
Other Ways to Say: Not all there, touched in the head.
4. Lost Your Marbles
Meaning: Gone crazy or insane.
In a Sentence: After days without sleep, he started acting like he’d lost his marbles.
Other Ways to Say: Flipped your lid, gone nuts.
5. Nuts About Something
Meaning: Extremely enthusiastic (sometimes irrationally).
In a Sentence: She’s nuts about cats — her entire house is full of cat stuff.
Other Ways to Say: Obsessed, crazy for.
6. Not Playing with a Full Deck
Meaning: Lacking intelligence or sanity.
In a Sentence: Anyone who swims with sharks for fun isn’t playing with a full deck.
Other Ways to Say: A few cards short, unbalanced.
7. A Screw Loose
Meaning: Slightly mentally unhinged.
In a Sentence: That guy has a screw loose if he thinks he can fly with cardboard wings.
Other Ways to Say: Loony, wacky.
8. Off the Rails
Meaning: Acting wild or irrationally.
In a Sentence: Ever since the breakup, he’s been completely off the rails.
Other Ways to Say: Spiraling, out of control.
9. Bonkers
Meaning: Crazy in a silly or wild way.
In a Sentence: That bonkers plan actually worked!
Other Ways to Say: Zany, loopy.
10. Gone Round the Bend
Meaning: Become mentally unstable.
In a Sentence: She’s gone round the bend if she thinks that dog can talk.
Other Ways to Say: Lost it, cracked up.
11. Batty
Meaning: Eccentric or slightly mad.
In a Sentence: That batty old lady talks to her plants like they’re people.
Other Ways to Say: Dotty, odd.
12. Cuckoo
Meaning: Crazy or insane.
In a Sentence: He’s totally cuckoo for trying to live in the woods alone.
Other Ways to Say: Nuts, off your nut.
13. Loco
Meaning: Slang for crazy (Spanish origin).
In a Sentence: You’d have to be loco to eat that many chilies.
Other Ways to Say: Mad, deranged.
14. Off the Wall
Meaning: Unconventional or bizarre.
In a Sentence: His off-the-wall sense of humor makes everyone laugh.
Other Ways to Say: Wacky, eccentric.
15. Daft
Meaning: Silly or mentally unbalanced (British slang).
In a Sentence: That was a daft idea — of course it didn’t work.
Other Ways to Say: Silly, ridiculous.
16. Cracked
Meaning: Mentally unstable.
In a Sentence: He’s cracked if he thinks ghosts are real.
Other Ways to Say: Bizarre, nuts.
17. Fruit Loop
Meaning: A crazy or eccentric person.
In a Sentence: Don’t mind her; she’s a bit of a fruit loop.
Other Ways to Say: Wacko, oddball.
18. Nut Job
Meaning: Someone who is considered mentally unstable.
In a Sentence: That guy climbing the billboard is a total nut job.
Other Ways to Say: Maniac, head case.
19. Loony Tunes
Meaning: Completely crazy.
In a Sentence: The way he acts during meetings is pure loony tunes.
Other Ways to Say: Bonkers, deranged.
20. Off One’s Head
Meaning: Acting irrationally or mentally disturbed.
In a Sentence: You must be off your head to try that stunt.
Other Ways to Say: Out of your mind, mental.
21. Wacko
Meaning: A crazy or irrational person.
In a Sentence: His wacko ideas never make any sense.
Other Ways to Say: Crackpot, lunatic.
22. Psycho
Meaning: Extremely mentally unstable (often dangerous).
In a Sentence: That movie villain is a complete psycho.
Other Ways to Say: Maniac, madman.
23. Gone Nuts
Meaning: Become crazy.
In a Sentence: Everyone thinks he’s gone nuts after quitting his job to become a mime.
Other Ways to Say: Flipped out, lost it.
24. Not Right in the Head
Meaning: Mentally unwell.
In a Sentence: Anyone who eats bugs on purpose is not right in the head.
Other Ways to Say: Mentally unstable, unbalanced.
25. As Crazy as a Loon
Meaning: Very crazy.
In a Sentence: That idea is as crazy as a loon!
Other Ways to Say: Nutty, mad.
26. Around the Twist
Meaning: Mentally disturbed or strange.
In a Sentence: She’s gone around the twist since she started seeing UFOs.
Other Ways to Say: Delusional, off-balance.
27. Totally Mental
Meaning: Extremely irrational or illogical.
In a Sentence: That stunt he pulled was totally mental.
Other Ways to Say: Bonkers, daft.
28. Flipped One’s Lid
Meaning: Lost control or became angry/crazy.
In a Sentence: He flipped his lid when they canceled the show.
Other Ways to Say: Lost it, blew a fuse.
29. Nuts in the Head
Meaning: Not mentally sound.
In a Sentence: That guy’s nuts in the head to believe in mermaids.
Other Ways to Say: Loopy, cracked.
30. Off the Deep End
Meaning: Become irrational or extreme.
In a Sentence: She went off the deep end after losing her job.
Other Ways to Say: Spiraled, lost her grip.
31. Gone Bananas
Meaning: Acting wild or irrational.
In a Sentence: The crowd went bananas when the band came out.
Other Ways to Say: Freaked out, went wild.
32. Kooky
Meaning: Strange in a fun or silly way.
In a Sentence: Her kooky fashion sense always draws attention.
Other Ways to Say: Eccentric, quirky.
33. Loopy
Meaning: Acting silly or mentally out of it.
In a Sentence: He was a bit loopy after staying up for two nights.
Other Ways to Say: Dizzy, strange.
34. Gone Gaga
Meaning: Obsessed or mentally deranged.
In a Sentence: He’s gone gaga over that new tech gadget.
Other Ways to Say: Infatuated, nuts.
35. Nutty as a Fruitcake
Meaning: Extremely eccentric or mad.
In a Sentence: That inventor is nutty as a fruitcake, but brilliant.
Other Ways to Say: Mad as a hatter, quirky.
36. In Cloud Cuckoo Land
Meaning: Out of touch with reality.
In a Sentence: He’s living in cloud cuckoo land if he thinks that plan will work.
Other Ways to Say: Unrealistic, dreaming.
37. Potty
Meaning: Slightly mad (British slang).
In a Sentence: She must be potty to paint her whole house pink.
Other Ways to Say: Loopy, silly.
38. Up the Wall
Meaning: Driven to madness or extreme frustration.
In a Sentence: These kids are driving me up the wall!
Other Ways to Say: Losing it, frantic.
39. Crazy Like a Fox
Meaning: Appears crazy but is actually clever.
In a Sentence: Don’t be fooled — he’s crazy like a fox.
Other Ways to Say: Cunning, sly.
40. Full-Blown Crazy
Meaning: Totally insane.
In a Sentence: That was a full-blown crazy idea — but it worked.
Other Ways to Say: Out of control, completely nuts.
41. Cray-Cray
Meaning: Slang for very crazy.
In a Sentence: That party last night was cray-cray!
Other Ways to Say: Wild, insane.
42. Wild Card
Meaning: Unpredictable person.
In a Sentence: You never know what she’ll do — she’s a wild card.
Other Ways to Say: Unpredictable, loose cannon.
43. Head Case
Meaning: A person with mental health issues or strange behavior.
In a Sentence: He’s a head case when it comes to organizing things.
Other Ways to Say: Neurotic, unstable.
44. Maniac
Meaning: Wild or dangerous person.
In a Sentence: He drives like a maniac on the highway.
Other Ways to Say: Lunatic, madman.
45. Out to Lunch
Meaning: Not mentally present.
In a Sentence: During the meeting, she seemed completely out to lunch.
Other Ways to Say: Spaced out, distracted.
46. Off in La-La Land
Meaning: Lost in imagination or not paying attention.
In a Sentence: He was off in la-la land during the entire lecture.
Other Ways to Say: Daydreaming, spaced out.
47. Losing It
Meaning: Becoming emotionally or mentally unstable.
In a Sentence: I’m losing it with all this stress at work.
Other Ways to Say: Breaking down, unraveling.
48. Out of One’s Mind
Meaning: Not thinking clearly.
In a Sentence: You must be out of your mind to say that in public!
Other Ways to Say: Delusional, irrational.
49. Nutcase
Meaning: A person who behaves irrationally.
In a Sentence: That guy who talks to pigeons is a nutcase.
Other Ways to Say: Wacko, loony.
50. Freak Show
Meaning: A wild or crazy situation.
In a Sentence: That party turned into a total freak show by midnight.
Other Ways to Say: Chaos, madness.
