pillow partner—(sl.) smb. with whom a person regularly has sex outside marriage:
- I can usually make use of a native pillow partner.
Note: The expression does not correlate in meaning with the compound bed-fellow—one’s companion or associate:
- The oddest of enemies might become bedfellows.
sleeping partner—
1. (also: dormant partner) a partner who does not take an active part in managing the business:
- He has been the sleeping partner who has supplied a great part of their capital.
2. (sl.) = pillow partner:
- Your sleeping partner would provide you with an alibi.