Definition of "foul play"

"I think there's been foul play," said Poole, hoarsely.

1886 January 5, Robert Louis Stevenson, Strange Case of Dr Jekyll and Mr Hyde, London: Longmans, Green, and Co.

An autopsy, pending a toxicology report, would determine the cause of death, the Los Angeles county medical examiner said. Foul play was not suspected, said Cap Scot Williams, who leads the city’s police robbery homicide division that is investigating Perry’s death.

2023 October 30, Sian Cain, “Friends stars release statement after death of Matthew Perry: ‘We were more than just castmates’”, in The Guardian‎