Pronunciation: (top'min"ō), [key]
—pl. (esp. collectively) -now, (esp. referring to two or more kinds or species) -nows.
any of several small, surface-swimming fishes of the egg-laying family Cyprinodontidae and the live-bearing family Poeciliidae, some of which are used in mosquito control.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.