Source : Webster's Revised Unabridged Dictionary (1913)

Mulatto \Mu*lat"to\, n.; pl. {Mulattoes}. [Sp. & Pg. mulato,
   masc., mulata, fem., of a mixed breed, fr. mulo mule, L.
   mulus. See {Mule}.]
   The offspring of a negress by a white man, or of a white
   woman by a negro, -- usually of a brownish yellow complexion.

Source : WordNet®

mulattoes
     See {mulatto}