a form of torture, typically used as an interrogation technique, in which a person is strapped head-down on a sloping board with the mouth and nose covered while water is poured over their face, causing them to experience a sensation similar to that of drowning
his lawyers told the court that he was subjected to waterboarding on more than 80 occasions
subject (someone) to the process of waterboarding
he was waterboarded and deprived of sleep