from The American Heritage® Dictionary of the English Language, 4th Edition
- n. Slang A person regarded as eccentric or irrational: "a catchy pop portrait of a wacko who talks to himself in French” ( Phoebe Hoban).
- adj. Wacky.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- adj. amusingly eccentric or irrational
- n. An amusingly eccentric or irrational person.
- interj. hurrah
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. a person who is regarded as eccentric or mad
Alteration of wacky.(American Heritage® Dictionary of the English Language, Fourth Edition)
wack(y) + -o (Wiktionary)