The Collaborative International Dictionary of English v.0.48:

Runcinate \Run"ci*nate\, a. [L. runcinatus, p. p. of runcinare
   to plane off, fr. runcina a plane.] (Bot.)
   Pinnately cut with the lobes pointing downwards, as the leaf
   of the dandelion.
   [1913 Webster]

WordNet (r) 3.0 (2006):

runcinate
    adj 1: having incised margins with the lobes or teeth pointing
           toward the base; as dandelion leaves