Source : Webster's Revised Unabridged Dictionary (1913)

Adulterous \A*dul"ter*ous\, a.
   1. Guilty of, or given to, adultery; pertaining to adultery;
      illicit. --Dryden.

   2. Characterized by adulteration; spurious. ``An adulterous
      mixture.'' [Obs.] --Smollett.

Source : WordNet®

adulterous
     adj 1: characterized by adultery; "an adulterous relationship";
            "extramarital affairs"; "the extracurricular
            activities of a philandering husband" [syn: {extramarital},
             {extracurricular}]
     2: not faithful to a spouse or lover; "adulterous husbands and
        wives"; "a two-timing boyfriend" [syn: {cheating(a)}, {two-timing(a)}]