One who does something stupid, annoying, or pointless.
One who asks questions they know the answer to simply to try and feel less stupid.
Anyone who fucks up.
*proffessor writes 5+5=10*
Prof: See, the result is 5.
That Guy: duh.. don't you mean the result is 10??
Everyone Else: Shut the fuck up dumbass, stop being that guy.