The Collaborative International Dictionary of English v.0.48:

Viscus \Vis"cus\, n.; pl. Viscera. [L., perhaps akin to E.
   viscid.] (Anat.)
   One of the organs, as the brain, heart, or stomach, in the
   great cavities of the body of an animal; -- especially used
   in the plural, and applied to the organs contained in the
   abdomen.
   [1913 Webster]

WordNet (r) 3.0 (2006):

viscus
    n 1: a main organ that is situated inside the body [syn:
         internal organ, viscus]