One who is confined in a prison.

An individual involuntarily confined in a penal institution, including persons: (1) sentenced under a criminal or civil statue; (2) detained pending arraignment, trial, or sentencing; and (3) detained in other facilities (e.g., for drug detoxification or treatment of alcoholism) under statutes or commitment procedures providing such alternatives to criminal prosecution or incarceration in a penal institution [45 CFR 46.303(c)].

a person who is confined; especially a prisoner of war

a person incarcerated in a prison or similar facility, typically for violating laws

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.

A person who is held in custody in prison• Sentencing Options

a captive," replied the fox-captain, strutting up and down with much dignity

A defendant who has been placed into custody or on bail.