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.]

The Collaborative International Dictionary of English v.0.48:

Black-eyed Susan \Black"-eyed` Su"san\ (Bot.)
   (a) The coneflower, or yellow daisy (Rudbeckia hirta).
   (b) The bladder ketmie.
       [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

black-eyed Susan
    n 1: tropical African climbing plant having yellow flowers with
         a dark purple center [syn: black-eyed Susan, black-eyed
         Susan vine, Thunbergia alata]
    2: annual weedy herb with ephemeral yellow purple-eyed flowers;
       Old World tropics; naturalized as a weed in North America
       [syn: flower-of-an-hour, flowers-of-an-hour, bladder
       ketmia, black-eyed Susan, Hibiscus trionum]
    3: the state flower of Maryland; of central and southeastern
       United States; having daisylike flowers with dark centers and
       yellow to orange rays [syn: black-eyed Susan, Rudbeckia
       hirta, Rudbeckia serotina]