especially: a man who is unfaithful to his wife or partner
… on a realistic level King is an incorrigible philanderer who deserts his gentle wife … Louise Westling
[Florenz] Ziegfeld's private life was messy. He was an outrageous philanderer who at one point kept a mistress in the same hotel he lived in with Anna Held. Alicia Metcalf Miller
Until then, public officials who were philanderers or alcoholics … pretty much operated with immunity from disclosure so long as their professional performance was unaffected. Tom Goldstein