prisonern.[F. prisonnier.]1. One who is confined in a prison.(Piers Plowman.)2. A person under arrest, or in custody, whether in prison or not; a person held in involuntary restraint; a captive; as, a prisoner at the bar of a court.(Bouvier.)Prisoner of Hope thou art, -- look up and sing. (Keble.)Prisoner's base. See Base, n., 24.()