Anilingus
Anilingus (also spelled analingus) is an oral and anal sex act (anal–oral contact or anal–oral sex) in which one person stimulates the anus of another by using their tongue or lips. The anus has a relatively high concentration of nerve endings and can be an erogenous zone, so the recipient may receive pleasure from external anal stimulation, whereas pleasure for the giver is usually based more on the principle of the act.