ThreadKiller

a biting wit seen on facebook that effectively kills the thread, regardless of topic. 45 comments might be flowing freely on a thread, and then this person comes in, and either through wit, political incorrectness or pure non sequitur, prohibits anyone else from posting to the thread, effectively 'killing it'

dude did you see that thread that john had on his page?

yeah it was great until that guy posted the cameltoe pic!

i know, what a threadkiller.