Green’s Dictionary of Slang

1. (US black) a plain tobacco cigarette, as opposed to a marijuana-filled one [its dimensions, which tend to be leaner than those of a marijuana cigarette].

1975

Wentworth & Flexner DAS.

2. (US gay) in pl., very tight trousers [abbr. Slim Jim n. (2)].

1972

(ref. to mid-1960s) B. Rodgers Queens’ Vernacular 53: overly tight pants. slims (mid ’60s).