The same thing as a dicksucker. Somebody who sucks on a dick. This word originated in 2001 on the campus of The University of Dayton in Ohio. An international student went off upon seeing that his chicken pot pie had been eaten, and he attacked the guilty party with a barrage of curse words. He managed to say just about every insult in the English language, and he even invented a new one: suckdicker. This word is much funnier if you can get an international student to say it in a fit of rage.
Mickey: "Who eat pot pie was mine!"
Scotty: "I ate it man I was hungry."
Mickey: "Scott, you faggot, mother of a fucker, bitch, asshole, shit, pussy, damnit Scott."
Scotty: "Fuck off loser."
Mickey: "You are a fuck, faggot fucker, son of bitch, suckdicker!"
Scotty:(walking out the door) "blow me asshole."