The Collaborative International Dictionary of English v.0.48:

nutsedge \nutsedge\, nut sedge \nut sedge\n.
   a widely distributed perennial sedge (Cyperus rotundus)
   having small edible nutlike tubers; also called nut grass.

   Syn: nutgrass, nut grass, Cyperus rotundus.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

nutsedge
    n 1: a widely distributed perennial sedge having small edible
         nutlike tubers [syn: nutgrass, nut grass, nutsedge,
         nut sedge, Cyperus rotundus]