Etheostomoid \E`the*os"to*moid\, a. [NL. etheostoma name of a genus + -oid.] (Zo["o]l.) 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}.