A cuckold

Dave, yes I got confused. The correct answer is cuckold.

The only time I heard the term cuckold was when it was used by a foreigner and I had to look it up. 

What Dan wrote was exactly right! 

Thanks guys For being so quick and helpful. I think cuckhold is the word I want to find since I am referring to the "husband" who is cheated by his wife rather than the other way around. Paramour is more like the man who is dating the unfaithful wife in this case. It's a question I have from my conversation class on the topic of relationship. And as a teacher I fall speechless when we talk about the man. Losing face. Thanks for your help again!

Lmao in America .. Typical thing to say would just be a cheater or they are doing adultery but then people would also give them SOOO many bad names just to cuss them out xD