noun, plural wack·os.

Also wack. an eccentric, strange, or odd person.


Origin of wacko

1970–75, Americanism; see wacky, -o
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

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Contemporary Examples of wacko

British Dictionary definitions for wacko



mad or eccentric

noun plural wackos

a mad or eccentric person

Word Origin for wacko

C20: back formation from wacky
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for wacko

extended form of wack, recorded from 1977.

Online Etymology Dictionary, © 2010 Douglas Harper