The Collaborative International Dictionary of English v.0.48:

paca \pa"ca\ (Pg. p[aum]"k[.a]; E. p[=a]"k[.a]), n. [Pg., from
   the native name.]
   1. (Zool.) A large burrowing South American rodent (Agouti
      paca syn. Cuniculus paca, formerly C[oe]logenys
      paca), having blackish brown fur, with four parallel rows
      of white spots along its sides; the spotted cavy. It is
      closely allied to the agouti and the Guinea pig and is
      highly esteemed as food.
      [1913 Webster]

WordNet (r) 3.0 (2006):

paca
    n 1: large burrowing rodent of South America and Central
         America; highly esteemed as food [syn: paca, Cuniculus
         paca]