IPA: //ˈpær.ə.mʌr//
KK: /ˈpærəˌmʌr/
A person with whom someone has a romantic relationship, often in secret or outside of marriage.
He was her secret paramour, and they met in hidden places.
Paramour → It is formed from "para-" (meaning beside or alongside) and "amour" (from Old French, meaning love). The word "paramour" refers to a lover, especially one in a secret or illicit relationship, suggesting a love that exists alongside another relationship.
Think of someone who loves 'beside' ('para-') another, which helps you remember that a 'paramour' is a secret lover.