cheat on

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.
See also: cheat, on
Farlex Dictionary of Idioms.

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.
See also: cheat, on
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs.

cheat on

Be sexually unfaithful to, as in They broke up right after she found he was cheating on her. [Colloquial; 1920s]
See also: cheat, on
The American Heritage® Dictionary of Idioms by Christine Ammer.

cheat on

v.
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.
See also: cheat, on
The American Heritage® Dictionary of Phrasal Verbs.
See also:
  • cheat on (someone or something)
  • cheat at
  • cheat at (something)
  • blued, screwed, and tattooed
  • screwed, blued, and tattooed
  • tattoo
  • shafted
  • shaft
  • get the shaft
  • get screwed