What is "swimming crab"

Swimming \Swim"ming\, a.

1. That swims; capable of swimming; adapted to, or used in, swimming; as, a swimming bird; a swimming motion.

2. Suffused with moisture; as, swimming eyes.

   Swimming bell (Zo["o]l.), a nectocalyx. See Illust. under Siphonophora.

   Swimming crab (Zo["o]l.), any one of numerous species of marine crabs, as those of the family Protunid[ae], which have some of the joints of one or more pairs of legs flattened so as to serve as fins.

n. Any of many marine crabs of the family Portunidae, whose hindmost legs are flattened into paddles.

n. marine crab with some legs flattened and fringed for swimming