From The Collaborative International Dictionary of English v.0.48 [gcide]:
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]
From WordNet (r) 3.0 (2006) [wn]:
lignite
n 1: intermediate between peat and bituminous coal [syn:
lignite, brown coal, wood coal]