Another word for ass. Find more ways to say ass, along with related words, antonyms and example phrases at masqueropa.net, the See definition of ass. ass · 1. countable noun An ass is an animal which is related to a horse but which is smaller and has long ears. · 2. countable noun If you describe someone as an. Chambers 20th Century Dictionary( / 1 vote)Rate this definition: Ass. as, n. a well-known quadruped of the horse family: (fig.) a dull, stupid fellow.—Asses'. Ass definition, a long-eared, slow, patient, sure-footed domesticated mammal, Equus asinus, related to the horse, used chiefly as a beast of burden. See more.