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1.
(verb construct) Indulging enthusiastically in one's favorite acts of sexual congress, esp. those activities most likely to appall mainstream society which one secretly enjoys best of all; wanton sexual gratification.

Standard usage limits definition to interactions with at least one other partner — but in hardship cases, this requirement may be waived to encompass solo practitioners so fugly they only get they freak on by theyselves.
I ain't sleep for shit last night, damn loud-ass skanky roommate up in there gettin' (her) freak on.

Long as you don't mind me getting (my) freak on before I bring her home, I be happy to take yo sister to the dance.

One often loses all track of time while getting one's freak on.
by Big Gus Dickus May 23, 2008