[madcat]

Cheating refers to the overt or covert breaking of rules to gain advantage in a competitive situation. The rules infringed may be explicit, or they may be from an unwritten code of conduct based on morality, ethics or custom, making the identification of cheating a subjective process. Cheating can refer specifically to marital infidelity. Someone who is known for cheating is referred to as a cheat in British English, and a cheater in American English.

http://en.wikipedia.org/wiki/Cheating