Green’s Dictionary of Slang

oscar n.1

[ety. unknown; ? play on Oscar Wilde + the ‘wild’ activity of sex or violence; or brandname Oscar Meyer, a popular US weiner (thus punning on weenie n.1 (4))]

1. (US black) the penis.

[US] ‘The Love Guide’ [comic strip] in B. Adelman Tijuana Bibles (1997) 144: Hold your oscar in your hand and open your eyes.

2. (US prison) a handgun.

[US]Goldin et al. DAUL 149/2: Oscar. (Rare) A pistol or revolver.
[UK]J. Morton Lowspeak.