The Collaborative International Dictionary of English v.0.48:

Clover \Clo"ver\ (kl[=o]"v[~e]r), n. [OE. claver, clover, AS.
   cl[=ae]fre; akin to LG. & Dan. klever, D. klaver, G. klee,
   Sw. kl["o]fver.] (Bot.)
   A plant of different species of the genus Trifolium; as the
   common red clover, Trifolium pratense, the white,
   Trifolium repens, and the hare's foot, Trifolium arvense.
   [1913 Webster]

   Clover weevil (Zool.) a small weevil (Apion apricans),
      that destroys the seeds of clover.

   Clover worm (Zool.), the larva of a small moth (Asopia
      costalis), often very destructive to clover hay.

   In clover, in very pleasant circumstances; fortunate.
      [Colloq.]

   Sweet clover. See Meliot.
      [1913 Webster]

WordNet (r) 3.0 (2006):

Trifolium pratense
    n 1: erect to decumbent short-lived perennial having red-purple
         to pink flowers; the most commonly grown forage clover
         [syn: red clover, purple clover, Trifolium pratense]