wack·o. A person regarded as eccentric or irrational: "a catchy pop portrait of a wacko who talks to himself in French" (Phoebe Hoban). adj. Wacky.

What does you're a wacko mean?

noun. variants: or less commonly whacko. Definition of wacko (Entry 2 of 2) : a person who is wacky also : psycho. Synonyms & Antonyms Example Sentences Learn More About wacko.

What does wacko mean in Australia?

wackonoun. An amusingly eccentric or irrational person.