freak out

From freak + out. 1960s countercultural slang.

freak out (plural freak outs)

1. (slang, 1960s counterculture) A positive experience with LSD or other psychedelic drug; (antonym) bummer, bum trip.

freak out (third-person singular simple present freaks out, present participle freaking out, simple past and past participle freaked out)

1. (slang, intransitive) To react (or cause to react) with extreme anger or fear to something to the extent that one loses one's composure or behaves irrationally; originally, 1960's countercultural term meaning to have a positive reaction or experience from the recreational, therapeutic or edificational use of a psychotropic – usually hallucinogenic or psychedelic – drug
   • 1991, Thelma and Louise (movie)

     Jimmy'll come in off the road, you won't be there, he'll freak out and call you a hundred thousand times...

2. (slang, transitive) To scare someone.
   • 2012 June 3, Nathan Rabin, “TV: Review: THE SIMPSONS (CLASSIC): “Mr. Plow” (season 4, episode 9; originally aired 11/19/1992)”, in (Please provide the book title or journal name)‎:

     Even the blithely unselfconscious Homer is more than a little freaked out by West’s private reverie, and encourages his spawn to move slowly away without making eye contact with the crazy man.

• (react with extreme anger or fear): set one's hair on fire

• (drugs): bum out