stub (a cigarette or cigar) out
Definition: to stop a cigarette or cigar from burning by pressing the end against something hard.
E.g.1: She stubbed her cigarette out and immediately lit up another one.
E.g.2: Stubbing his cigarette out in the ashtray, he blew the smoke out through his nose and left the pub.
This phrasal verb can be separated. (E.g. 1 and 2)