The Collaborative International Dictionary of English v.0.48:

Citric \Cit"ric\, a. [Cf. F. citrique. See Citron.] (Chem.)
   Of, pertaining to, or derived from, the citron or lemon; as,
   citric acid.
   [1913 Webster]

   Citric acid (Chem.), an organic acid, C3H4OH.(CO2H)3,
      extracted from lemons, currants, gooseberries, etc., as a
      white crystalline substance, having a pleasant sour taste.
      [1913 Webster]

WordNet (r) 3.0 (2006):

citric acid
    n 1: a weak water-soluble acid found in many fruits (especially
         citrus fruits); used as a flavoring agent