noun
paramour
PAIR-uh-moor/ˈpærəmʊr/
A lover, especially in a secret or illicit relationship.
The lover embraces a paramour in the doorway while anxiously watching for the unsuspecting partner.

Etymology
The phrase “with love” or “passionately” became a name for a beloved person or sweetheart. Its once broader affectionate meaning narrowed chiefly to a secret or illicit lover.
In context
her new paramour killed a man in an illegal duel and had to flee Versailles. … Julie … joined her lover on the run.
An encounter with the jealous boyfriend of one of his paramours left him with a distinctive scar
More examples
- He hides letters from his paramour in a locked drawer.
- The novel follows two paramours who risk everything for love.
- Her husband discovers that her paramour is an old friend.
Forms
paramour · paramours
Similar words
- lover
- A broader term that does not necessarily suggest secrecy.
- sweetheart
- Usually suggests affectionate romance rather than an illicit relationship.