Source : Webster's Revised Unabridged Dictionary (1913)

Culm \Culm\ (k[u^]lm), n. [L. culmus stalk, stem; akin to
   calamus. See{Halm}.] (Bot.)
   The stalk or stem of grain and grasses (including the
   bamboo), jointed and usually hollow.

Culm \Culm\, n. [Perh. from W. cwlm knot or tie, applied to this
   species of coal, which is much found in balls or knots in
   some parts of Wales: cf. OE. culme smoke, soot.] (Min.)
   (a) Mineral coal that is not bituminous; anthracite,
       especially when found in small masses.
   (b) The waste of the Pennsylvania anthracite mines,
       consisting of fine coal, dust, etc., and used as fuel. --
       Raymond.

Source : WordNet®

culm
     n : stem of plants of the Gramineae