The act of being rear-ended (anal sex) that is so satisfying it makes the receiver scream.
Man, he fucked me so good it was sphincterlicious.
When something that you think should taste like ass, ends up tasting pretty good. Or anything metaphorically equal. As in you thought that was going to suck... but it didn't!
"Well Joe I thought having sex with that chubby girl was going to be a bad time but it turned out to be sphincterlicious."