The Collaborative International Dictionary of English v.0.48:

Agouti \A*gou"ti\, Agouty \A*gou"ty\ ([.a]*g[=oo]"t[i^]), n. [F.
   agouti, acouti, Sp. aguti, fr. native name.] (Zool.)
   1. A rodent of the genus Dasyprocta, about the size of a
      rabbit, peculiar to South America and the West Indies. The
      most common species is the Dasyprocta agouti.
      [1913 Webster]

   2. the color of the agouti[1], a grayish-brown of grizzled
      texture; -- used especially to describe the color of the
      fur of a strain of mice. Also used attributively.
      [PJC]