Source : Webster's Revised Unabridged Dictionary (1913)

Coneflower \Cone"flow`er\, n.
   Any plant of the genus {Rudbeckia}; -- so called from the
   cone-shaped disk of the flower head. Also, any plant of the
   related genera {Ratibida} and {Brauneria}, the latter usually
   known as {purple coneflower}.

Source : WordNet®

coneflower
     n 1: any of various plants of the genus Rudbeckia cultivated for
          their large usually yellow daisies with prominent
          central cones
     2: any of various perennials of the eastern United States
        having thick rough leaves and long-stalked showy flowers
        with drooping rays and a conelike center