prisoner

• pris‧on‧er [countable]
• 1 someone who is kept in a prison as a legal punishment for a crime or while they are waiting for their trial [↪ guard, imprison]:
• Relationships between the staff and the prisoners are good.
• Prisoners here only serve short sentences.
• remand prisoner British English (=someone who is in prison waiting for their trial)
• The organization is arguing for the release of political prisoners(=people in prison because of their political opinions).
• 2 someone who is taken by force and kept somewhere [= captive]
• hold/keep somebody prisoner
• The guerillas kept her prisoner for three months.
• He was being held prisoner.
• Our pilot was taken prisoner.
• The army advanced, taking 200,000 prisoners.
• 3 someone who is in a place or situation from which they cannot escape:
• He is a prisoner of his own past.

Definition from the Longman Dictionary of Contemporary English
Advanced Learner's Dictionary.