The Collaborative International Dictionary of English v.0.48:

Brassica \Bras"si*ca\, prop. n. [L., cabbage.] (Bot.)
   A genus of plants embracing several species and varieties
   differing much in appearance and qualities: such as the
   common cabbage (Brassica oleracea), broccoli, cauliflowers,
   etc.; the wild turnip (Brassica campestris); the common
   turnip (Brassica rapa); the rape or coleseed (Brassica
   napus), etc.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Brassica napus
    n 1: Eurasian plant cultivated for its seed and as a forage crop
         [syn: rape, colza, Brassica napus]