Green’s Dictionary of Slang

(orig. US) a mad person, an eccentric; also as adj.

1972		Playboy Apr. 82: DeVreer had sort of a running open house for crazos over there, all the local eccentrics like Vampira [HDAS].
1984		D. Jenkins Life Its Ownself (1985) 28: Those cities were perfect for your ‘mondo, craze-o, leftist derelicts.’.
2002		C. Hitchens in Love, Poverty and War (2005) 161: I noticed at airports that the name [i.e. Ozark] was ‘krazo’ spelled backwards.