1. the fleshy part of the human body that you sit on
he deserves a good kick in the butt|are you going to sit on your fanny and do nothing?
2. a pompous fool
3. hardy and sure-footed animal smaller and with longer ears than the horse
4. slang for sexual intercourse
5. A quadruped of the genus Equus (E. asinus), smaller than the horse, and having a peculiarly harsh bray and long ears. The tame or domestic ass is patient, slow, and sure-footed, and has become the type of obstinacy and stupidity. There are several species of wild asses which are swift-footed.