Source : Webster's Revised Unabridged Dictionary (1913)

Marmoset \Mar"mo*set`\, n. [F. marmouset a grotesque figure, an
   ugly little boy, prob. fr. LL. marmoretum, fr. L. marmor
   marble. Perhaps confused with marmot. See {Marble}.]
   (Zo["o]l.)
   Any one of numerous species of small South American monkeys
   of the genera {Hapale} and {Midas}, family {Hapalid[ae]}.
   They have long soft fur, and a hairy, nonprehensile tail.
   They are often kept as pets. Called also {squirrel monkey}.

Source : WordNet®

marmoset
     n : small soft-furred South American and Central American monkey
         with claws instead of nails