Green’s Dictionary of Slang

1. (US black) a hat.

1965		Esquire July 44: Hats [...] are called brims.
1972		O. Hawkins Ghetto Sketches 12: Adjusting and readjusting his large, white-rimmed burgundy brim.
1980		E. Folb Runnin’ Down Some Lines 110: Some terms that talk primarily about specific clothing items, such as [...] brims (hats), kicks (shoes), lizards (lizard-skin shoes), leather pieces (leather jackets), and so on.
1992		UGK ‘Cocaine in the Back of the Ride’ 🎵 Khaki pants, black sweater with the U.G.K. brim.
1998		B. Gifford Sinaloa Story 178: You ever see a vulture wear a brim?

2. the flesh at the base of one’s glans penis.

1997

Roger’s Profanisaurus in Viz 87 Dec. n.p.: brim n. The skirting around the base of one’s helmet (qv).