1. influencing one’s own or others’ outcomes by deceit, trickery, or other unfair maneuvers. Because cheating is disruptive to maintaining a variety of social relationships, human beings and other animals have developed strategies to detect and punish it.

2. in evolutionary psychology, using asocial strategies to gain an evolutionary advantage. For example, males of some species who have formed an exclusive pair bond with a female may nonetheless seek to mate with other females so as to increase their chances of producing offspring.

3. in reciprocal altruism, the failure of an individual to aid another individual who has provided assistance in the past.

4. see infidelity. —cheat vb., n.