what does trial by ordeal mean

Trial by ordeal was a judicial practice in which the guilt or innocence of the accused was determined by subjecting them to a painful or dangerous physical test, such as holding a hot iron or being thrown into a river. The belief was that if the accused survived the ordeal, they were innocent, and if they did not, they were guilty. This practice was common in medieval Europe and other parts of the world until the 18th century.