Source : Webster's Revised Unabridged Dictionary (1913)

Baboon \Bab*oon"\, n. [OE. babewin, baboin, fr.F. babouin, or
   LL. babewynus. Of unknown origin; cf. D. baviaan, G. pavian,
   baboon, F. babin lip of ape, dogs, etc., dial. G. b["a]ppe
   mouth.] (Zo["o]l.)
   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.

Source : WordNet®

baboon
     n : large terrestrial monkeys having doglike muzzles