From The Collaborative International Dictionary of English v.0.48 :
Orca \Or"ca\ ([^o]r"k[.a]), prop. n.
killer+whale+({Orcinus+orca">The killer whale ({Orcinus orca).
[PJC]
From 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]