ass

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. Any of several hoofed mammals of the genus Equus, resembling and closely related to the horses but having a smaller build and longer ears, and including the domesticated donkey.
2. n. A vain, self-important, silly, or aggressively stupid person.
3. n. The buttocks.
4. n. The anus.
5. n. Vulgar Slang Sexual intercourse.

Century Dictionary and Cyclopedia

1. n. A solidungulate quadruped of the family Equidœ, the Equus asinus. This animal has long ears, a short maue, and a tail covered with long hairs at the end. It is usually ash-colored, with a black cross over the shoulders, formed by a longitudinal and a transverse dark streak. The tame or domestic ass is patient, and carries a heavy burden. It is slow, but very sure-footed, and for this reason very useful on rough, steep, and hilly ground. The ass is supposed to be a native of central Asia (by Darwin and others, of Abyssinia), where vast troops roam over the great deserts in a wild state. The wild ass is a fine fleet animal, and is accounted the noblest game in Persia, where its flesh is prized as venison is with us. The domesticated ass has become the type of obstinacy and stupidity. See jackass.
2. n. Any wild species of the subgenus Asinus, as the dziggetai or hemione, onager, etc.
3. n. A dull, heavy, stupid fellow; a dolt; a fool; a blockhead.
4. n. A post in the bridge of a pulp-vat on which the mold is placed to drain.
5. n. Ashes.
6. n. A unit of weight in use in different parts of Germany until the adoption of the metric system. It was equal to 5 centigrams, or three quarters of a grain troy.

Wiktionary

1. n. Any of several species of horse-like animals, especially Equus africanus, often domesticated and used a beast of burden.
2. n. slang A stupid person.
3. n. vulgar, slang Buttocks.
4. n. vulgar, slang, uncountable Sex.
5. n. vulgar, slang Anus.
6. n. slang Used in similes to express something bad or unpleasant.
7. n. slang Used after an adjective to indicate extremes or excessiveness.
8. n. slang One's self or person, chiefly their body.

GNU Webster's 1913

1. n. (Zoöl.) A quadruped of the genus Equus (Equus 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.
2. n. A dull, heavy, stupid fellow; a dolt.

WordNet 3.0

1. n. hardy and sure-footed animal smaller and with longer ears than the horse
2. n. a pompous fool
3. n. the fleshy part of the human body that you sit on
4. n. slang for sexual intercourse