The Collaborative International Dictionary of English v.0.48:

mandrill \man"drill\ (m[a^]n"dr[i^]l), n. [Cf. F. mandrille, Sp.
   mandril, It. mandrillo; prob. the native name in Africa. Cf.
   Drill an ape.] (Zool.)
   A large West African baboon (Papio sphinx syn. Mandrillus
   sphinx, formerly Cynocephalus mormon syn. Papio mormon).
   The adult male has, on the sides of the nose, large, naked,
   grooved swellings, conspicuously striped with blue and red.
   It is an endangered species.
   [1913 Webster +PJC]

WordNet (r) 3.0 (2006):

mandrill
    n 1: baboon of west Africa with a bright red and blue muzzle and
         blue hindquarters [syn: mandrill, Mandrillus sphinx]