A more thorough explanation:

Definition: Double adultery refers to adultery between two individuals who are both married to other people.

Adultery is defined as voluntary sexual intercourse between a married person and someone other than their spouse. While it is considered a crime in some jurisdictions, it is rarely prosecuted. In states that allow fault divorce, proof of adultery can be used as grounds for divorce. A court may also use proof of adultery to reduce the offending spouse's share of marital property in a property division. Judges used to view adultery as a reason to deny the offending spouse primary custody of a child in a child-custody dispute, but today only the negative impact of immoral behavior on the child is considered relevant.

Other types of adultery include:

• Incestuous adultery: Adultery committed by closely related individuals.
• Open and notorious adultery: Adultery in which the parties reside together publicly, as if married, and the community is generally aware of the living arrangement and the fact that the couple is not married.
• Single adultery: Adultery in which only one of the individuals is married.

Example: John and Jane are both married to other people, but they have been having an affair with each other. This is an example of double adultery.

Explanation: John and Jane are both committing adultery because they are married to other people and engaging in sexual activity with each other. Since they are both married to other people, this is an example of double adultery.