Green’s Dictionary of Slang

1. an eccentric, a madman.

1965		H.S. Thompson letter 4 Nov. in Proud Highway (1997) 546: There was not much point in your visiting a potential flip-out, in Big Sur or anywhere else.
1979		Eble Campus Sl. Mar. 3: flip out – the cause of shock or amazement: She’s a real flip-out – she dresses like she lives in the twenties.

2. attrib. use of sense 1.

1972

C. Bukowski Erections, Ejaculations etc. 48: Don’t put me in no flip-out cage. I just want to laze around.

3. a crazy, uncontrolled reaction to a drug or a situation.

1968		L. Wolf Voices from the Love Generation 277: flip-out. Mental derangement; strange behaviour.
1969		R.R. Lingeman Drugs from A to Z (1970).