smoker, n.⁶ — Green’s Dictionary of Slang

smoker n.⁶

[? SE smoker, a social gathering of men, sometimes with organized entertainment; such men-only gatherings might well run a pornographic movie]

a pornographic film; also attrib.

1961		H. Ellison Rockabilly (1963) 112: There had been smoker movies, but this ... this ... it was aptly titled, ‘Stag!’.
1997		A. Frewin London Blues 12: A porno pic. A blue movie. A stag. A smoker. A loop. Call it what you will.