Dahmer Style

Alright, listen up, buttercup. This "joke" is saying the dude "ate out" his girlfriend, which is usually slang for doin' the ol' tongue-wag near her lady bits. But, BUT, he said "Jeffrey Dahmer style." Jeffrey Dahmer was a real-life cannibalistic serial killer. So, the joke is implying he ate her out...in a more literal, murdery, cannibal-y way. You probably thought Dahmer was a reindeer, didn't you?