The Collaborative International Dictionary of English v.0.48:

leaf cutter \leaf cutter\, leaf-cutter \leaf-cutter\n. (Zool.)
   Any one of various species of wild bees of the genus
   Megachile, which cut rounded pieces from the edges of
   leaves, or the petals of flowers, to be used in the
   construction of their nests, which are made in holes and
   crevices, or in a leaf rolled up for the purpose. Among the
   common American species are Megachile brevis and Megachile
   centuncularis. Called also rose-cutting bee.

   Syn: leaf-cutting bee, leaf-cutter bee.
        [1913 Webster + WordNet 1.5]

WordNet (r) 3.0 (2006):

leaf-cutter
    n 1: bee that cuts rounded pieces from leaves and flowers to
         line its nest [syn: leaf-cutting bee, leaf-cutter,
         leaf-cutter bee]