The Collaborative International Dictionary
Ommateum
Ommateum \Om`ma*te"um\, n.; pl. Ommatea. [NL., fr. Gr. ?, ?, the eye.] (Zo["o]l.) A compound eye, as of insects and crustaceans.
Wiktionary
ommateum
n. (context zoology English) A compound eye, as of insects and crustaceans.