An instance in which the tongue is rubbed in a circular motion around someone else's sphincter.

"Oh, why that's when you put your legs behind your head and have someone lick your ass!"
~Cartman's mom, the south park movie.

Also known as Rimming.

The surprisingly pleasurable act of licking or having ones own sphincter licked.

The process of performing a Rim Job can be fraught with dangers such as stumbling across clingons, the rimee releasing an air biscuit, or simply encountering a particularly unhygienic ring piece.

someone's tongue in your asshole, for sexual pleasure.

Oral-anal stimulation for the purpose of sexual gratification. Enjoyed by those who have tried it, feared by those who have not. Married couples typically overlook this in their foreplay.

to lick somebodys asshole

using your tongue to fondle the outside (and inside) of your partner's clean ass hole in a circular or lapping motion