Any one of several small American cyprinodont fishes of the genus Fundulus and allied genera. They live equally well in fresh and brackish water, or even in the sea. They are usually striped or barred with black. Called also minnow, and brook fish. See Minnow. [1913 Webster]
killifish, n.
1 any small fresh- or brackish-water fish of the family Cyprinodontidae, many of which are brightly coloured.
2 a brightly-coloured tropical aquarium fish, Pterolebias peruensis.