any of a family (Trionychidae) of aquatic turtles of North America, Asia, and Africa, with a soft, oval, leathery shell; esp., a North American genus (Trionyx) common in the Mississippi drainage
See soft-shelled turtle in American Heritage Dictionary 4
noun
Any of various freshwater turtles of the family Trionychidae, having a flat carapace covered with leathery skin and a fleshy elongated snout.