Smap refers to the act of spamming an internet forum without the intent to be annoying. Rather it is done for comic relief and to chase away forum trolls.
The word was first used during a drunken post in the JTS at the famous nforcershq.com.
SMAP (verb) - The act of slapping a person after applying one's smegma (A whitish sebaceous secretion that collects between the glans penis and foreskin or in the vulva) to their hand.
Jeremy: I'll kick your ass!
Brian: Well I'll smap you in the fucking face.