2. when used literally, would most likely mean (though no one knows who would honestly do this) to use the tongue and lips to actually suck someone else's intercourse. to lick and/or suck the area where the penis is entering the vagina.
1. Elizabeth: Donnie, you're such a fuckass!
Donnie: Oh yeah? Well, you can go suck a fuck!
2. "Man, I thought a threesome would be hot, but all that crazy bitch did was suck our fuck!"