From The Collaborative International Dictionary of English v.0.48:
orc \orc\ ([^o]rk), n. [L. orca, a kind of whale: cf. F. orque.]
1. (Zool.) Any of several cetaceans, especialy the grampus
(Grampus griseus) of the dolphin family. [Written also
ork and orch.] --Milton.
[1913 Webster]
An island salt and bare,
The haunt of seals, and orcs, and sea-mews' clang.
--Milton (Par.
Lost xi. 835).
2. (Mythology) A mythical monster of varying descriptions; an
ogre.
[PJC]
Goblins, hobgoblins, and orcs of the worst
description. --J. J.
Tolkien (The
Hobbit)
3. The orca.
[PJC]