Source : Webster's Revised Unabridged Dictionary (1913)

Madwort \Mad"wort`\, n. (Bot.)
   A genus of cruciferous plants ({Alyssum}) with white or
   yellow flowers and rounded pods. {A. maritimum} is the
   commonly cultivated sweet alyssum, a fragrant white-flowered
   annual.

Alyssum \A*lys"sum\, n. [NL., fr. Gr. ?, name of a plant, perh.
   fr. 'a priv. + ? raging madness.] (Bot.)
   A genus of cruciferous plants; madwort. The {sweet alyssum}
   ({A. maritimum}), cultivated for bouquets, bears small,
   white, sweet-scented flowers.

Source : WordNet®

alyssum
     n 1: any garden plant of the genus Alyssum having clusters of
          small yellow or white flowers [syn: {madwort}]
     2: a genus of the family Cruciferae [syn: {genus Alyssum}]