ADULTEROUS
adulterous, cheating, two-timing
(adjective) not faithful to a spouse or lover; “adulterous husbands and wives”; “a two-timing boyfriend”
adulterous, extramarital, extracurricular
(adjective) characterized by adultery; “an adulterous relationship”; “extramarital affairs”; “the extracurricular activities of a philandering husband”
Source: WordNet® 3.1
Adjective
adulterous (comparative more adulterous, superlative most adulterous)
Of, or characterized by adultery.
Source: Wiktionary
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: Webster’s Unabridged Dictionary 1913 Edition