Rumpilingus
Eating another person's ass to provide sexual pleasure. Usually a result of a large chemical or alcohol intake that leaves you feeling so wild and horny you just wanna do EVERYTHING.
I came home from that kegger and I was so blotto I think I performed rumpilingus on my girl.
or
On prom night, we did everything shy of rumpilingus.
or
On prom night, we did everything shy of rumpilingus.