1. (adj)adulterous, cheating(a), two-timing(a) not faithful to a spouse or lover "adulterous husbands and wives"; "a two-timing boyfriend"
2. (adj)cheating(a), dirty, foul, unsporting, unsportsmanlike violating accepted standards or rules "a dirty fighter"; "used foul means to gain power"; "a nasty unsporting serve"; "fined for unsportsmanlike behavior"
Definition of 'cheating'
