wackyEnglishOxford Dictionary of Englishwacky /ˈwaki / (also whacky) ▸ adjective ( wackier, wackiest; whackier, whackiest) informal funny or amusing in a slightly odd or peculiar way: a wacky chase movie. – DERIVATIVES wackily /ˈwakɪli / (also whackily) adverb wackiness /ˈwakinɪs / (also whackiness) noun– ORIGIN mid 19th century (originally dialect): from the noun whack + -y1.