Meaning of the word "have an affair with" in English

What does "have an affair with" mean in English? Explore the meaning, pronunciation, and specific usage of this word with Lingoland.

have an affair with

US /hæv ən əˈfɛr wɪð/
UK /hæv ən əˈfɛə wɪð/

Idiom

to have a sexual relationship with someone who is not your husband, wife, or regular partner

Example:
It was rumored that he had an affair with his secretary.
She discovered her husband had an affair with her best friend.