Definitions
American Heritage® Dictionary of the English Language, Fourth Edition
- adj. Slang Eccentric or irrational: a wacky person.
- adj. Slang Crazy; silly: a wacky outfit.
Wiktionary
WordNet 3.0
- adj. informal or slang terms for mentally irregular
- adj. ludicrous, foolish
Etymologies
- Variant of whacky, probably from the phrase out of whack; see whack. (American Heritage® Dictionary of the English Language, Fourth Edition)
Examples
“Wild incomptence can also work ... or just plain wacky/random things (see: nobody expects the spanish inquisition!) # Wingson 16 Apr 2009 at 7: 57 pm”
Superhero Nation: how to write superhero novels and comic books » Some Suggestions for Humor-Writers
“Dressed in wacky clothes, says funny stuff like, “I like pizza.” and “I got a wallet.””
“Kim Possible, Pinkie and the Brain, Invader Zim and many other comedies threw in wacky, wacky plots from time to time.”
Superhero Nation: how to write superhero novels and comic books » Tom’s Review Forum
“Q: Your characters are basically nice people caught in wacky scenarios that are mostly due to their own frailties and quirks.”
Writer Unboxed » Blog Archive » AUTHOR INTERVIEW: Katie Fforde
“It's a fish out of water story, with would-be heroes coming to terms with new abilities in wacky ways!”
“Mentioning a Velez-type or a player like Johnson around the same time as Albert Pujols or Jake Peavy can sometimes result in wacky numbers.”
“It would be very, very bad advice - sometimes crazy, misguided bad, resulting in wacky, embarrassing Three's Company-like scenarios - sometimes viciously, heinously bad resulting in devastating, life-crushing misery.”
“These newsroom characters are regarded less as role models than as holy fools whose wisdom, no matter how wacky, is still magical and oracular.”
“China uses the war on terror to justify its persecution of people in wacky cults like Falun Gong and the cultural genocide of the peace-loving Tibetans.”
“HAMMER: And this is why I used the word wacky earlier.”
Lists
These user-created lists contain the word ‘wacky’.
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UK - slang
chin wag, arse about, bollock, starkers, sweet Fanny Adams, skive, shufti, codswallop, rhyming slang, bollocks, nookie, skew-whiff and 208 more...
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Bonkers
List for old and new terms and phrases meaning crazy, nuts, batty, prone to extreme nervousness, etc.
bonkers, crazy, nuts, batty, batchy, bats in the belfry, scatty, crackers, windy, gone crackers, cracked, dingo and 92 more...
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Mentally irregular
Words for the mentally irregular
bonkers, unhinged, batshit crazy, cognitive dissonance, apophenia, undone, loony, unsound, deranged, a bit off the beam, daft, stark ravin' mad and 65 more...
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magoosh1
aberration, aboveboard, abysmal, ace, affable, aghast, alacrity, ambiguous, ambivalent, ameliorate, amenable, amiable and 215 more...
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Fun Words
Words that are fun to say....
gobbledygook, jings, crivens, hullabaloo, wheech, brouhaha, pizzazz, harum-scarum, namby-pamby, pussyfoot, frippery, pitter-patter and 333 more...
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artoparts's Words
illation, finite, edify, abide, abrade, vouch, amiss, vociferate, perusing, techantiquery, rigamarole, holon and 615 more...
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vinyl's Words
deliverator, finna, metric fuckton, fag, hyphy, ginormous, sacrilicious, fantabulous, macaca, n-word, pterodactyl, genious and 560 more...
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adjectives
sartorial, saucy, wieldy, wuthering, dilapidated, rough-and-ready, flabbergasted, ravishing, seminal, snooty, galore, scrumptious and 386 more...
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the favourites
These are words that I like; either because they sound amazing, mean pretty things, seem particularly suited to their assigned definition, or just have good mouthfeel. The best ones embody some com...
tatterdemalion, alpenglow, dapple, defenestrate, wacky, lissom, lithe, whisper, madcap, magniloquent, whimsy, sallow and 208 more...
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Just 'cause I like 'em, W
washboard, winterbourne, winze, wirble, waterway, windrow, winceyette, waft, whiffletree, wheelbarrow, whicker, wacky and 170 more...
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Magoosh
menace, injunction, juggernaut, refrain, mnemonic, abysmal, grueling, ace, gregarious, amiable, wacky, esoteric and 201 more...
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loonie
Inspired by Peter Reading's "Euphemisms".
crackers, potty, loony, bonkers, nutty, screwy, ga-ga, dull, strange, do-lally, dopey, silly and 83 more...
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W is for Wellies
My W Words
woolworth, wonky, watusi, wordpunk, whistle punk, wretch, with bells on, walkie-talkie, wocka wocka, wench, wordsmith, wanderlust and 55 more...
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of me
words I would use to describe myself
ambidextrous, bibliophile, creative, dogmatic, energetic, fixated, generous, hyper, intelligent, jabbering, kvetching, lyrical and 48 more...
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Random as Possible
just be random
wombat, nargles, isn't it with a g, gnargles, gargle, rawr, lion, kipper, tea, english, no, it's nargles ..., moo and 68 more...
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The Runaways (2010)
Words from a 2010 'The Runaways' film.
skanky, wacky, bitchen, prowler, halt, women’s lib, stash, commotion, heckler, roadie, varmint, vertigo and 8 more...
Tweets
Looking for tweets for wacky.

yarb This word has come to connote self-conscious, court-jester-style buffoonery, embarrassing to all concerned.
A good example of the older, more straightforward sense of 'weird', 'absurd' or 'unusual' is the 1974 Dr Seuss book "Wacky Wednesday". Nov 16, 2007