foul play

foul play
ˌfoul ˈplay noun [uncountable]
1. if the police think someone’s death was caused by foul play, they think that person was murdered:
    The police said they had no reason to suspect foul play.
    Detectives have not ruled out foul play.
2. an action that is dishonest, unfair, or illegal, especially one that happens during a sports game