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cheat on (someone or something)
1. To act deceptively or unfairly while completing a task or participating in a competition. I can't believe that Katie cheated on the test—I always thought she was an honest person.
2. To be unfaithful to one's romantic partner. Well, I heard that Jane cheated on Rob, and that's really why they're getting divorced.
cheat on someone
to commit adultery; to be unfaithful to one's spouse or lover. "Have you been cheating on me?" cried Mrs. Franklin. He was caught cheating on his wife.
Be sexually unfaithful to, as in They broke up right after she found he was cheating on her. [Colloquial; 1920s]
1. To behave fraudulently during some process or activity: The teacher caught the student cheating on the test.
2. To be unfaithful to someone, especially a spouse or lover: I hired a private detective to see if my spouse was cheating on me.