The Collaborative International Dictionary of English v.0.48:

Viscera \Vis"ce*ra\, n.,
   pl. of Viscus.
   [1913 Webster]

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):

viscera
    n 1: internal organs collectively (especially those in the
         abdominal cavity); "`viscera' is the plural form of
         `viscus'" [syn: viscera, entrails, innards]