To cheat on a spouse is to deprive them of sexual energy you should reserve for them, assuming they have a sex drive
Cheating on a spouse means you have compromised their financial needs, or if they require your time, or any other element, and you deprive them of it.
If your spouse has no interest in sex and you can find time to have a same sex encounter, I didn't think consider it cheating. It actually HELPS the marriage, as it takes away from tension and bitterness over not having your needs met, or putting someone in a position to have to force himself/herself to do something s/he really doesn't want to do.
Consider the need for food. If you go home and you're hungry, and your wife won't prepare a meal for you, you still have to eat, and can go out and get food somewhere else, whether you pay for it, or someone else cooks you a meal. Now replace the need for food with the need for sex, and it really comes down to the same thing.
I consider 2 buds on the side an extension of what you would do with your own body, just being projected onto another person. So you get together with a buddy for a while and you play with each others cocks, and you go home to your wives. How is that cheating, assuming your wife doesn't want sex when you get home, but you have no energy left for her.
"Well you're lying about where you said you were or who you were with". So be honest. Say you are hanging out with a friend for a while. You actually don't have to lie, while still maintaining respectable confidentiality.