The Collaborative International Dictionary of English v.0.48:

Fumaric \Fu*mar"ic\, a. (Chem.)
   Pertaining to, or derived from, fumitory (Fumaria
   officinalis).
   [1913 Webster]

   Fumaric acid (Chem.), a widely occurring organic acid,
      extracted from fumitory as a white crystallline substance,
      C2H2(CO2H)2, and produced artificially in many ways, as
      by the distillation of malic acid; boletic acid. It is
      found also in the lichen, Iceland moss, and hence was also
      called lichenic acid.
      [1913 Webster]

WordNet (r) 3.0 (2006):

fumaric acid
    n 1: a colorless crystalline acid with a fruity taste; used in
         making polyester resins