Burrowing crab of American coastal regions having one claw much enlarged in the male WordNet 3.0 & Open English WordNet

The fiddler crab or calling crab may be any of more than one hundred species of semiterrestrial marine crabs in the family Ocypodidae, well known for their sexually dimorphic claws; the males' major claw is much larger than the minor claw, while the females' claws are both the same size. Wikipedia

A species of crab found in parts of the Atlantic and Pacific oceans Wikipedia Disambiguation

A genus of crab in which the male has one hugely enlarged claw (genus Uca). Wiktionary

Uca (genus of crab in which males have one oversized claw). Wiktionary (translation)