Source : Webster's Revised Unabridged Dictionary (1913)

Ligule \Lig"ule\ (-[-u]l), n. [L. ligula, lingula, little
   tongue, dim. of lingua tongue : cf. F. ligule.]
   1. (Bot.)
      (a) The thin and scarious projection from the upper end of
          the sheath of a leaf of grass.
      (b) A strap-shaped corolla of flowers of Composit[ae].

   2. (Anat.) A band of white matter in the wall of fourth
      ventricle of the brain.

Source : WordNet®

ligule
     n : (botany) any appendage to a plant that is shaped like a
         strap