The Collaborative International Dictionary of English v.0.48:

Rye \Rye\ (r[imac]), n. [OE. rie, reie, AS. ryge; akin to Icel.
   rugr, Sw. r[*a]g, Dan. rug, D. rogge, OHG. rocco, roggo, G.
   rocken, roggen, Lith. rugei, Russ. roje, and perh. to Gr.
   'o`ryza rice. Cf. Rice.]
   1. (Bot.) A grain yielded by a hardy cereal grass (Secale
      cereale), closely allied to wheat; also, the plant
      itself. Rye constitutes a large portion of the breadstuff
      used by man.
      [1913 Webster]

   2. A disease in a hawk. --Ainsworth.
      [1913 Webster]

   Rye grass, Italian rye grass, (Bot.) See under Grass.
      See also Ray grass, and Darnel.

   Wild rye (Bot.), any plant of the genus Elymus, tall
      grasses with much the appearance of rye.
      [1913 Webster]

WordNet (r) 3.0 (2006):

wild rye
    n 1: any of several grasses of the genus Elymus