1. To extinguish a cigarette, cigar, or some other smoking material by stamping the burning end against a surface; stub something out: When the "No Smoking" sign lit up, we snubbed out our cigarettes. I took the cigarette and snubbed it out on the wall before the teacher saw me.
2. Slang To kill someone; murder someone: The gangsters snubbed the witness out. The mobsters snubbed out the competition.