Green’s Dictionary of Slang

freak v.2

[freak n.1 (7)]

1. [1960s+] to have adventurous sex; to have anal intercourse.

2. [1980s+] (US campus, also freak all over, freak on) to dance in a highly sexual manner, to simulate sex on the dance-floor.

3. [1990s+] to have sexual intercourse.

4. [2000s] to excite (sexually).

5. [2000s] (US drugs) to disguise a marijuana cigarette by wrapping it in a ‘legitimate’ cigar wrapper.

In phrases

freak it (v.)

to act in an unrestrained manner.

freak it up (v.)

[1970s] (US gay) to behave extravagantly, whether sexually or socially.