The Collaborative International Dictionary of English v.0.48:

Glume \Glume\ (gl[=u]m), n. [L. gluma hull, husk, fr. glubere to
   bark or peel: cf. F. glume or gloume.] (Bot.)
   The bracteal covering of the flowers or seeds of grain and
   grasses; esp., an outer husk or bract of a spikelet. --Gray.
   Glumella

WordNet (r) 3.0 (2006):

glume
    n 1: small dry membranous bract found in inflorescences of
         Gramineae and Cyperaceae