The Collaborative International Dictionary of English v.0.48:

Brachyura \Brach`y*u"ra\, n. pl. [NL., fr. Gr. brachy`s short +
   o'yra` tail.] (Zool.)
   A group of decapod Crustacea, including the common crabs,
   characterized by a small and short abdomen, which is bent up
   beneath the large cephalo-thorax. [Also spelt Brachyoura.]
   See Crab, and Illustration in Appendix.
   [1913 Webster] Brachyural

WordNet (r) 3.0 (2006):

Brachyura
    n 1: an order of crustaceans (including true crabs) having a
         reduced abdomen folded against the ventral surface [syn:
         Brachyura, suborder Brachyura]