The Collaborative International Dictionary of English v.0.48:

Geranium \Ge*ra"ni*um\ (j[-e]*r[=a]"n[i^]*[u^]m), n. [L., fr.
   Gr. gera`nion, from ge`ranos crane: cf. F. g['e]ranium. See
   Crane, n.]
   [1913 Webster]
   1. (Bot.) A genus of plants having a beaklike torus or
      receptacle, around which the seed capsules are arranged,
      and membranous projections, or stipules, at the joints.
      Most of the species have showy flowers and a pungent odor.
      Called sometimes crane's-bill.
      [1913 Webster]

   2. (Floriculture) A cultivated pelargonium.
      [1913 Webster]

   Note: Many plants referred to the genus Geranium by the
         earlier botanists are now separated from it under the
         name of Pelargonium, which includes all the commonly
         cultivated "geraniums", mostly natives of South Africa.
         [1913 Webster]

WordNet (r) 3.0 (2006):

geranium
    n 1: any of numerous plants of the family Geraniaceae