Source : Webster's Revised Unabridged Dictionary (1913)

Bract \Bract\, n. [See {Bractea}.] (Bot.)
   (a) A leaf, usually smaller than the true leaves of a plant,
       from the axil of which a flower stalk arises.
   (b) Any modified leaf, or scale, on a flower stalk or at the
       base of a flower.

   Note: Bracts are often inconspicuous, but sometimes large and
         showy, or highly colored, as in many cactaceous plants.
         The spathes of aroid plants are conspicuous forms of
         bracts.

Source : WordNet®

bract
     n : a modified leaf or leaflike part just below and protecting
         an inflorescence