Since brother ZamanH as well as other members intend one xpanding their difference about what is considered cheating for both men and women even in different subject forums I was hoping to address that subject here. I've given my understanding of what infidelity is in regards to marital affairs so I hope this helps again when I remind you all on my position. In regards to cheating there are different ways of cheating such as: cheating on taxes, cheating on games, cheating on counting etc.
Cheating not only includes being a liar but it also includes vain desires such as: self-indulgence, self-gratification and self-exaltation. I have to agree with Zaman on one point because of culture a lot of times how men and women approach each other depends on the evironment. He claims that Western culture is sinful and that because the explouitation of women (i.e The showing of half-naked women) and men in Western culture it makes sin open for everyone. To some extent theere is truth in this. Yes in Western society there is a sense of exploitation of both men and women yes there is a sense of open sexual indulgence yes there are laws which makes Godlessness acceptable. Yes there is a taint of immorality in Western society.
But like how some Muslims view other doctrines because there is a taint in society shouldn't make all of society bad. For example since Pre-Islamic Arabia the whole of society (or at least majority of it) believed in paganism. This was the norm and many people believed this would bring about blessings and fortune and what not. Now many of us wouldn't dare not believe that our prophet was originally a pagan just because his society was. The same with judging western culture.
The problem with infidelity is not whats on the outside but the inside of a person. If a man cheats on his wife sexually he does so by his own doing. Consciously if he is a Muslim man he understands what he is doing is wrong and its a sin. Consciously he knows what he's doing is a transgression on his marriage. If he is with one woman of course this is considered an extra-martial affair. Even if he is married to more than one woman if he has an extra-marital affair outside his current contractual obligation then they are all affairs and they are all cheating.
There is a slight difference because for women there are no multiple husbands (I'm not sure if there is any law within Shari'ah law that states a woman can have multiple husbands) and I'm sure if there is a limitation on this this is due to culture. For women the same rule applies. Any transgression out of a contractual obligation is considered cheating on the basis of taking advantage of situation and/self-indulgence. Regardless whether a woman cheats or a man cheats the ends themselves are equivalent because it personally relates to the person who acts them out. So please nough with the degrees of cheating because they are nothing more than trangression on our own limitations.