The Collaborative International Dictionary of English v.0.48:

Rudbeckia \Rud*beck"i*a\, n. [NL. So named after Olaf Rudebeck,
   a Swedish botanist.] (Bot.)
   A genus of composite plants, the coneflowers, consisting of
   perennial herbs with showy pedunculate heads, having a
   hemispherical involucre, sterile ray flowers, and a conical
   chaffy receptacle. There are about thirty species,
   exclusively North American. Rudbeckia hirta, the
   black-eyed Susan, is a common weed in meadows.
   [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

Rudbeckia
    n 1: North American perennial herbs with showy cone-shaped
         flower heads [syn: Rudbeckia, genus Rudbeckia]