word (ex. nubivagant), language (ex. Portuguese), topic (ex. love),
part of speech (ex. noun), origin (ex. origin: Latin), first letter (ex. A)
…well, I have many words for a cheater. But not many of them are polite enough to use in this answer, if you know what I mean.
Philanderer works for a man who cheats, but it’s not exclusive to cheaters. It can also mean a man who chases women and has many insignificant sexual relationships.
Quisling is a good one. It means traitor, especially during war, but I’ve also known it used to describe a cheater. Spoken aloud, it has a nice undertone of disgust to it—doesn’t it just sound sort of slimy? Appropriate, I think.
Fun etymology fact of the day: Despite the appearance, the words “adult” and “adultery” come from two different Latin roots, so they aren’t related at all.