Green’s Dictionary of Slang

1. (UK Und.) a snack.

1801

Sporting Mag. Nov. XIX 88/2: He therefore directed Knowles, under the pretence of going for a smag, to fetch the constables.

2. (US campus) a cigarette.

1997–2002

Hope College ‘Dict. of New Terms’ 🌐 smag n. Cigarette. Common name for cigarette used by young smokers.