Green’s Dictionary of Slang

1. (US campus) a spot, a pimple.

1967–8

Baker et al. CUSS.

2. (UK teen) a cigarette.

2019

N. Lezard in New Statesman 28 June-4July 58/3: I ask [my son] to teach me young person’s slang. ‘Blem’, apparently is a cigarette.