The Collaborative International Dictionary of English v.0.48:

Alouatta \Alouatta\, Alouatte \Al`ou*atte"\, n. [Of uncertain
   origin.] (Zool.)
   One of the several species of howling monkeys of South
   America. See Howler[2].
   [1913 Webster + WordNet 1.5]

WordNet (r) 3.0 (2006):

Alouatta
    n 1: howler monkeys [syn: Alouatta, genus Alouatta]