The Collaborative International Dictionary of English v.0.48:

Lignite \Lig"nite\ (l[i^]g"n[imac]t), n. [L. lignum wood: cf. F.
   lignite.] (Min.)
   Mineral coal retaining the texture of the wood from which it
   was formed, and burning with an empyreumatic odor. It is of
   more recent origin than the anthracite and bituminous coal of
   the proper coal series. Called also brown coal, wood
   coal.
   [1913 Webster]

WordNet (r) 3.0 (2006):

lignite
    n 1: intermediate between peat and bituminous coal [syn:
         lignite, brown coal, wood coal]