What is "fighting crab"

Fiddler \Fid"dler\, n. [AS. fi[eth]elere.]

1. One who plays on a fiddle or violin.

2. (Zo["o]l.) A burrowing crab of the genus Gelasimus, of many species. The male has one claw very much enlarged, and often holds it in a position similar to that in which a musician holds a fiddle, hence the name; -- called also fiddler crab, calling crab, soldier crab, and fighting crab.

3. (Zo["o]l.) The common European sandpiper ( Tringoides hypoleucus); -- so called because it continually oscillates its body.

   Fiddler crab. (Zo["o]l.) See Fiddler, n., 2.