The Collaborative International Dictionary of English v.0.48:

Maleic \Ma*le"ic\, a. [Cf. F. mal['e]ique. See Malic.] (Chem.)
   Pertaining to, or designating, an acid of the ethylene series
   (maleic acid), metameric with fumaric acid and obtained by
   heating malic acid.
   [1913 Webster]