baboon

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Any of several large terrestrial African and Arabian monkeys of the genus Papio, having an elongated doglike muzzle and bare calluses on the buttocks.
• noun Slang A brutish person; a boor.

from The Century Dictionary.

• noun A quadrumanous animal of the old world, of the subfamily Cynopithecinæ, and especially of either of the genera Cynocephalus (or Papio) and Mandrilla (or Mormon).

from the GNU version of the Collaborative International Dictionary of English.

• noun (Zoöl.) One of the Old World Quadrumana, of the genera Cynocephalus and Papio; the dog-faced ape. Baboons have dog-like muzzles and large canine teeth, cheek pouches, a short tail, and naked callosities on the buttocks. They are mostly African. See mandrill, and chacma, and drill an ape.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun zoology Mostly African primates. One of the Old World Quadrumana, of the genera Cynocephalus and Papio; the dog-faced ape. Baboons have dog-like muzzles and large canine teeth, cheek pouches, a short tail, and naked callosities on the buttocks.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun large terrestrial monkeys having doglike muzzles