"stifler" in the noun sense
1. stifler, smotherer
a person who stifles or smothers or suppresses
"he is a real conversation stifler"
"I see from all the yawn smotherers that it is time to stop"
Source: WordNet® (An amazing lexical database of English)
Princeton University "About WordNet®."
WordNet®. Princeton University. 2010.
View WordNet® License