Green’s Dictionary of Slang

lunachick n.

[pun on SE lunatic; note the NYC punk band the Lunachicks, founded 1987]

(US campus) a crazy woman.

[US]College Sl. Research Project (Cal. State Poly. Uni., Pomona) 🌐 Lunachick (noun) A girl who is basically psycho, or exhibits behavior that is out of the ordinary for the given situation.