Detention by the police. Detain Law and Legal Definition. Detain generally means to prevent from proceeding; to restrict freedom of movement. In criminal law, detain means to hold a person in custody, often for purposes of questioning. A law enforcement officer needs to have a reasonable suspicion of unlawful activity to detain a person. Yes, your record should show you were detained. A police officer may briefly detain a person, without a warrant, if the officer has reasonable suspicion that the person is involved in a crime, and an officer may use reasonable force to effect that detention. As nouns the difference between detainee and prisoner is that detainee is someone who is detained, especially in custody or confinement while prisoner is a person incarcerated in a prison, while on trial or serving a sentence. Definition of detention · Detention of a suspect · Indefinite detention. Types of detention, detained, when can police detain you, how long can you be detained, preventive detention, detention synonym, detention centre, detention in hindi.