Well since everyones posting for anti-cheating (probably cause there are "girls" on the forum you need to impress) i will go ahead and play devils advocate. Before you get mad (scrub) i am in a relationship, we live together and i work to support her, so everyone has their own stuff get over it. I love her and we have worked out our own relationship so here goes my DA's 2 cents:
1. Its only cheating if you get caught, just like speeding the law only applies when their is someone to enforce it.
2. Cheating implies breaking a set of rules. Obviously you are all assuming that the rules for a relationship are crisp and clear but in reality everyone is just humans and relationships are even more stringent based on that fact. For a relationship you should clearly define what the "rules" are with you partner, if you fail to mention that flirtation or even *** with another person is NOT ok then they are not technically cheating for there was no rule to be broken.
3. To simply define cheating in black and white terms is silly, again do to your own humanity. You say I cheat if i have *** with a girl that is not my girlfriend. What about threesomes, swaps, 2 guys 1 girl? all of these are sexually deviant acts that a fairly large part of the population participates in. Dont believe me, check craigslist, hell even google swinger clubs i bet there is 1 by you. As a couple the most important thing is to understand what you expect from each other. In my opinion a relationship is something i have with someone who i want to give the world to, and as such, occasionally deviant desires arise from either side. Commonly people ignore these feelings and it results in what many call "cheating". In my DA's opinion if you are not comfortable with who your partner is, even sexually, then you are the one cheating yourself.