The Collaborative International Dictionary of English v.0.48:

Adulterate \A*dul"ter*ate\, v. t. [imp. & p. p. Adulterated;
   p. pr. & vb. n. Adulterating.] [L. adulteratus, p. p. of
   adulterare, fr. adulter adulterer, prob. fr. ad + alter
   other, properly one who approaches another on account of
   unlawful love. Cf. Advoutry.]
   [1913 Webster]
   1. To defile by adultery. [Obs.] --Milton.
      [1913 Webster]

   2. To corrupt, debase, or make impure by an admixture of a
      foreign or a baser substance; as, to adulterate food,
      drink, drugs, coin, etc.
      [1913 Webster]

            The present war has . . . adulterated our tongue
            with strange words.                   --Spectator.
      [1913 Webster]

   Syn: To corrupt; defile; debase; contaminate; vitiate;
        sophisticate.
        [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

adulterating \adulterating\ adj.
   1. making impure or corrupt by virtue of extraneous origin;
      -- of impurities. the adulterating effect of extraneous
      materials purifying

   Syn: adulterant
        [WordNet 1.5]

   2. making impure or corrupt by adding extraneous materials;
      -- of people.

   Syn: adulterant.
        [PJC]

WordNet (r) 3.0 (2006):

adulterating
    adj 1: making impure or corrupt by adding extraneous materials;
           "the adulterating effect of extraneous materials" [syn:
           adulterating, adulterant] [ant: purifying]