E`the*os"to*moid (?), a. [NL. etheostoma name of a genus + -oid.] (Zoöl.) Pertaining to, or like, the genus Etheostoma. -- n. Any fish of the genus Etheostoma and related genera, allied to the perches; -- also called darter. The etheostomoids are small and often bright-colored fishes inhabiting the fresh waters of North America. About seventy species are known. See Darter.