AID PRAYER, English law. A petition to the court calling in help from another person who has an interest in the matter in dispute. For example, a tenant for life, by the courtesy or for years, being impleaded, may pray aid of him in reversion; that is, desire the court that he may be called by writ, to allege what he thinks proper for the maintenance of the right of the person calling him, and of his own. F. N. B. 60; Cowel.