A tom cat is a slang term for a philanderer.
philanderer, antecedents
A philanderer is a married man who has affairs with women other than his wife.
Bob is cheating on his wife, he's such a philanderer.
The slang term for philanderer is "player" or "womanizer."
An archaic term was "rake." The usual term today is philanderer.
Philanderer
philanderer
No, he is not a philanderer (a man who has many casual sexual relationships) but he is a philantropist (someone who donates money for good causes).
John Willoughby
It was quite disconcerting to me to learn that my own father is a notorious serial philanderer. Unlike many of today's 'wannabes', Al Capone was a notorious gangster.
Don Juan, Lothario, Prince Charming,lady's man, lady-killer, philanderer,playboy, Casanova, womanizer