The Collaborative International Dictionary of English v.0.48:

Saki \Sa"ki\ (s[=a]"k[i^]), n. [Cf. F. & Pg. saki; probably from
   the native name.] (Zool.)
   Any one of several species of South American monkeys of the
   genus Pithecia. They have large ears, and a long hairy tail
   which is not prehensile.
   [1913 Webster]

   Note: The black saki (Pithecia satanas), the white-headed
         (Pithecia leucocephala), and the red-backed, or
         hand-drinking, saki (Pithecia chiropotes), are among
         the best-known.
         [1913 Webster]