Bedfellow (noun)

A person who shares a bed, typically a sexual partner.

Origin:

Bedfellow, from bed + fellow, is a person who shares a bed, typically a sexual partner.

Examples:

1. He was embarrassed to introduce his bedfellow to his friends.
2. She was not pleased with her husband's bedfellows.
3. He had a revolving door of bedfellows.
4. She was his bedfellow for many years.
5. He had a bedfellow for the night.