The Collaborative International Dictionary of English v.0.48:

Dandelion \Dan"de*li`on\, n. [F. dent de lion lion's tooth, fr.
   L. dens tooth + leo lion. See Tooth, n., and Lion.]
   (Bot.)
   A well-known plant of the genus Taraxacum (Taraxacum
   officinale, formerly called Taraxacum Dens-leonis and
   Leontodos Taraxacum) bearing large, yellow, compound
   flowers, and deeply notched leaves.
   [1913 Webster]

WordNet (r) 3.0 (2006):

dandelion
    n 1: any of several herbs of the genus Taraxacum having long tap
         roots and deeply notched leaves and bright yellow flowers
         followed by fluffy seed balls [syn: dandelion,
         blowball]