The Collaborative International Dictionary of English v.0.48:

Orca \Or"ca\ ([^o]r"k[.a]), prop. n.
   The killer whale (Orcinus orca).
   [PJC]

WordNet (r) 3.0 (2006):

Orcinus orca
    n 1: predatory black-and-white toothed whale with large dorsal
         fin; common in cold seas [syn: killer whale, killer,
         orca, grampus, sea wolf, Orcinus orca]