Oral stimulation (kissing, nibbling, tonguing, etc.) of a partner's ear. Following the pattern of "cunnilingus," the word comes from Latin auris 'ear' + lingere 'lick.'
Janisha: Terry gave me some sweet aurilingus last night! She said I tasted like chestnuts.
Xiuying: Hold on, you mean oral sex?
Janisha: Aural, yeah. It was hot.
This is different than a rimjob. A rimjob would, however, be a precursor to anilingus. It is the act of plunging one's tongue into the anal cavity of your sexual partner and then swirling and thrusting aforementioned tongue in an effort to make said partner happy.
It is well advised to wash the anus that is to be pleasured thoroughly (and perhaps even douche) before attempting this.
Anilingus is the "scientific" term for applying ones mouth to another ones asshole. Then plunging ones tongue deep within the anal cavity, and swirling it 'round; giving one's partner sexual pleasure.