Swimming crab

from WordNet (r) 3.0 (2006)
swimming crab
    n 1: marine crab with some legs flattened and fringed for
         swimming
    
from The Collaborative International Dictionary of English v.0.48
Swimming \Swim"ming\, a.
   1. That swims; capable of swimming; adapted to, or used in,
      swimming; as, a swimming bird; a swimming motion.
      [1913 Webster]

   2. Suffused with moisture; as, swimming eyes.
      [1913 Webster]

   {Swimming bell} (Zool.), a nectocalyx. See Illust. under
      {Siphonophora}.

   {Swimming crab} (Zool.), any one of numerous species of
      marine crabs, as those of the family {Protunidae}, which
      have some of the joints of one or more pairs of legs
      flattened so as to serve as fins.
      [1913 Webster]
    

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