detainer n[Anglo-French detenoure , from detenir to restrain, detain, from Old French, from Latin detinere ]
1 : the act of keeping something in one's possession
: unlawful detainer
2 : detention in custody
3 : a notification sent by a prosecutor, judge, or other official advising a prison official that a prisoner is wanted to answer criminal charges and requesting continued detention of the prisoner or notification of the prisoner's impending release compare extradition
Source: Merriam-Webster's Dictionary of Law ©1996. Merriam-Webster, Incorporated. Published under license with Merriam-Webster, Incorporated.