Wiktionary
a. (alternative spelling of wacky English)
WordNet
adj. pungent adjectives of disesteem; "gave me a cockamamie reason for not going"; "wore a goofy hat"; "a silly idea"; "some wacky plan for selling more books" [syn: cockamamie, cockamamy, goofy, sappy, silly, wacky, zany, unreasonable]
informal or slang terms for mentally irregular; "it used to drive my husband balmy" [syn: balmy, barmy, bats, batty, bonkers, buggy, cracked, crackers, daft, dotty, fruity, haywire, kooky, kookie, loco, loony, loopy, nuts, nutty, round the bend, around the bend, wacky]
Wikipedia
Whacky was a British comic strip published in the British comic book magazine Cor!! and ran in the comic from its first issue on 6 June 1970 until 29 September 1973 - some 9 months before it was merged with Buster. It started as a half page strip but proved popular and was given a full page several weeks later. It was created and drawn by Mike Lacey.
Usage examples of "whacky".
I believe our next great evolutionary advancement will be some kind of whacky gestalten outgrowth of the body and the beaner.
This consisted of making a first reading of all those letters and cards of mysterious authorship and often unintelligible purpose that senior officers, for whose eyes are reserved only the least whacky winnowings, are pleased to call “communications from members of the public”.