To have sex a dead person of the same sex as you. In other words, gay necrophilia. Can be used as a derogitory phrase to someone who is creepy as hell.
Guy 1: That guy's so creepy, he's always alone, and yesturday I saw him eat things out of the trash can! Guy 2: Wtf? Really? Guy 1: Yeah, he's so fuckin creepy. Guy 2: Hahah, he probably has necrofagia! Guy: Hahahahaha!! Yeah probably!!
by Xero _ Manifest January 14, 2011