The Collaborative International Dictionary of English v.0.48:

Vetch \Vetch\ (v[e^]ch), n. [Also fitch; OE. ficche, feche, for
   veche, OF. veche, vecce, vesche, vesce, F. vesce, fr. L.
   vicia.] (Bot.)
   Any leguminous plant of the genus Vicia, some species of
   which are valuable for fodder. The common species is Vicia
   sativa.
   [1913 Webster]

   Note: The name is also applied to many other leguminous
         plants of different genera; as the chichling vetch, of
         the genus Lathyrus; the horse vetch, of the genus
         Hippocrepis; the kidney vetch (Anthyllis
         vulneraria); the milk vetch, of the genus
         Astragalus; the licorice vetch, or wild licorice
         (Abrus precatorius).
         [1913 Webster]

WordNet (r) 3.0 (2006):

vetch
    n 1: any of various climbing plants of the genus Vicia having
         pinnately compound leaves that terminate in tendrils and
         small variously colored flowers; includes valuable forage
         and soil-building plants

Moby Thesaurus II by Grady Ward, 1.0:

54 Moby Thesaurus words for "vetch":
   algae, autophyte, bean, bracken, brown algae, climber, conferva,
   confervoid, creeper, diatom, fern, fruits and vegetables, fucus,
   fungus, grapevine, green algae, gulfweed, herb, heterophyte, ivy,
   kelp, legume, lentil, liana, lichen, liverwort, mold, moss,
   mushroom, parasite, parasitic plant, pea, perthophyte,
   phytoplankton, planktonic algae, plant families, puffball, pulse,
   red algae, rockweed, rust, saprophyte, sargasso, sargassum,
   sea lentil, sea moss, sea wrack, seaweed, smut, succulent,
   toadstool, vine, wort, wrack