The Collaborative International Dictionary of English v.0.48:

Macrura \Ma*cru"ra\, n. pl. [NL., fr. Gr. ? long + ? tail.]
   (Zool.)
   A subdivision of decapod Crustacea, having the abdomen
   largely developed. It includes the lobster, prawn, shrimp,
   and many similar forms. Cf. Decapoda.
   [1913 Webster]