adultery

Short definition from Wiktionary

Noun

1. 1
   Sexual intercourse by a married person with someone other than their spouse. See more synonyms at Thesaurus:cuckoldry
2. 2
   Lewdness or unchastity of thought as well as act, as forbidden by the sixth/seventh commandment; sinful sexual behavior as a category.
3. 3
   Faithlessness in religion.
4. 4
   The fine and penalty formerly imposed for the offence of adultery.
5. 5
   The intrusion of a person into a bishopric during the life of the bishop.
6. 6
   Adulteration; corruption.
7. 7
   Injury; degradation; ruin.