He's a philanderer.

She's in total denial about her husband's philandering.

“Where did you get such miserable cargo, blinky?” “Rather, where are you carrying that debauched lot, you philanderer?”

Philandering is immoral.

Double Indemnity" is the title of a classic 1944 film noir, in which a philandering insurance salesman (Fred MacMurray) and a housewife (Barbara Stanwyck) plot to murder her husband, but to make it look like an accident, in order to collect on an insurance policy that will pay double the value in case of accidental death.

Tom is a philanderer.

Tom's a philanderer.

Though she was angry and hurt, she decided to turn a blind eye to her husband's philandering.