/ Dictionary / Index W wacko: Meaning and Definition of Find definitions for: wack•o Pronunciation: (wak'ō), [key] — n., pl. adj. wack•os, —n. an eccentric, strange, or odd person. —adj. wacky. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: wacko (Thesaurus) wacked-out wacky Related Content Daily Word Quiz: reclusive Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language