Green’s Dictionary of Slang

freak v.3

[abbr. freak out v.]
(orig. drugs/hippie)

1. to lose psychological control, whether enjoyably or otherwise, as the result of drugs, usu. hallucinogens; usu. as freaking.

[US]R.R. Lingeman Drugs from A to Z (1970) 97: freak [...] (1) to hallucinate, implying a grotesque, grandiose, perhaps bizarrely beautiful or abnormally horrifying distortion of consciousness.
[US]E.E. Landy Underground Dict. (1972).
[US]Eble Campus Sl. Apr. 4: freak – to act out of control.
[Aus]L. Redhead Rubdown [ebook] I’m not a freak, I just like to freak.
[US]C. Stella Rough Riders 25: She half naked in that robe [...] Kincaid went off, man. The Indian freaked.

2. (also freak one’s mind) to worry someone, to disturb, to cause severe anxiety (the extent of the disturbance varies totally as to context) (cf. freak out v. (2)).

[Aus]B. Humphries Barry McKenzie [comic strip] in Complete Barry McKenzie (1988) 94: You freak me grandpa.
[US]R. Stone Hall of Mirrors (1987) 225: ‘No, no,’ the girl said. ‘It’ll freak him.’.
[Aus]Lette & Carey Puberty Blues 59: It freaked me and I ran outside.
[US]Eble Campus Sl. Fall 3: freak my mind – have a shocking, puzzling, different mental experience: ‘Talking to that man really freaked my mind’.
[UK]M. Collins Keepers of Truth 146: Pete turned his head and listened to the cries. He said, ‘That always freaked me, them animals.’.

3. to worry, to be worried, to be severely anxious.

[US]C. McFadden Serial 28: Martha was particularly freaked when she learned [...] that Harvey was now involved with Carol. [Ibid.] 73: Kate and Harvey would have freaked if they knew she was hitching.
[US]Eble Campus Sl. Apr. 4: freak – act excessively nervous.
[UK]Guardian G2 24 Aug. 14: Should we be freaked by these possibly guileless images?
[UK]Guardian G2 23 Sept. 12: I [...] freaked myself sick with apprehension.
[Aus]T. Winton ‘Small Mercies’ in Turning (2005) 94: Your parents know you’re here? Yeah. They’re freaking.
[UK](con. 1980s) I. Welsh Skagboys 448: Molly’s freaked by it [i.e. an anecdote] and Tom chivalrously attempts to distract her.

4. to act in an emotional, melodramatic manner; thus freaked adj., emotionally overwhelmed.

[Aus]B. Humphries Barry McKenzie [comic strip] in Complete Barry McKenzie (1988) 44: They’ll really freak.
[US](con. 1960s) R. Price Wanderers 186: The regulars were [...] shrieking and freaking like a strung-out Greek chorus.
[US]E. Folb Runnin’ Down Some Lines 175: I freaked! Started runnin’ through the projects, yellin’, ‘Pigs after me!’.
[UK](con. 1950s–60s) in G. Tremlett Little Legs 32: They just freak.
[UK]T. Blacker Kill Your Darlings 288: Poor Dad. No wonder he was freaked.
[US]J. Ellroy ‘Jungletown Jihad’ in Destination: Morgue! (2004) 352: He humps homos. [...] The fruitcake Freddies freak.
[US]Codella and Bennett Alphaville (2011) 336: ‘Fuck you! I’ve killed people for less!’ ‘Don’t fucking freak, yo, I’ll get you the rest [of the money]’.
[US]J. Stahl OG Dad 5: I was shooting Mexican tar [...] freaking when the nurse banged on the door and told me the baby was coming.

5. (US gay) to be uninhibited, esp. at a party.

[US]B. Rodgers Queens’ Vernacular 85: freak [...] 4. to be delightfully uninhibited; to have an uproarious time at a party.

6. (US black) to perform.

[US]Source July 40: The way we write we leave it open so we could freak it a different way next time.
[US]L. Stavsky et al. A2Z 37/2: They was freakin’ the beats and movin’ the house.

In compounds

freak attack (n.)

(US teen) a state of extreme tension.

[US]Chevy Valentine Blog Archive 19 Sept. [Internet] Last night I managed to turn what should have been a perfectly lovely evening with beer and pool into a freak attack. Well nobody knew I had a freak attack except me.