Acharya Prashant explains that the definition of cheating depends entirely on the plane upon which a relationship exists: physical, mental, or spiritual. In a purely physical relationship, the contract is based on the mutual exchange of pleasure and the availability of the body. If a partner seeks physical pleasure elsewhere, it is considered cheating because the body was the sole foundation of the relationship. The speaker notes that if a person is absolutely offended by physical infidelity, it reveals that their relationship was fundamentally and exclusively physical, regardless of how they might label it.