Anilingus

Anilingus (from the Latin "anus" + "-lingus", from "lingere", "to lick", variantly spelled "analingus",) is the oral and anal sex act in which a person licks the anus of another by using the mouth, including lips, tongue, or teeth. It is also called anal–oral contact and anal–oral sex, and is additionally known by slang names.
Nicknames include: rimming, rim job, eating ass or tossing the salad.