The Collaborative International Dictionary of English v.0.48:

Margaric \Mar*gar"ic\, a. [Cf. F. margarique. See Margarite.]
   Pertaining to, or resembling, pearl; pearly.
   [1913 Webster]

   Margaric acid.
   (a) (Physiol. Chem.) A fatty body, crystallizing in pearly
       scales, and obtained by digesting saponified fats (soaps)
       with an acid. It was formerly supposed to be an
       individual fatty acid, but is now known to be simply an
       intimate mixture of stearic and palmitic acids.
   (b) (Chem.) A white, crystalline substance, C17H34O2 of the
       fatty acid series, intermediate between palmitic and
       stearic acids, and obtained from the wax of certain
       lichens, from cetyl cyanide, and other sources. Called
       also heptadecanoic acid.
       [1913 Webster]

WordNet (r) 3.0 (2006):

margaric acid
    n 1: a colorless crystalline synthetic fatty acid [syn:
         margaric acid, heptadecanoic acid]