The Collaborative International Dictionary of English v.0.48:
Detainer \De*tain"er\ (-[~e]r), n.
1. One who detains.
(a) The keeping possession of what belongs to another;
detention of what is another's, even though the
original taking may have been lawful. Forcible
detainer is indictable at common law.
(b) A writ authorizing the keeper of a prison to continue
to keep a person in custody.
Bouvier's Law Dictionary, Revised 6th Ed (1856):
DETAINER. 1. The act of keeping a person against his will, or of keeping
goods or property. All illegal detainers of the person amount to false
imprisonment, and may be remedied by habeas corpus.
2.-2. A detainer or detention of goods is either lawful or unlawful;
when lawful, the party having possession of them cannot be deprived of it.
The detention may be unlawful, although the original taking was lawful; as
when goods were distrained for rent, and the rent was afterwards paid; or
when they 'Were pledged, and the money borrowed, and interest were
afterwards paid; in these, and the like cases, the owner should make a
demand, (q.v.) and if the possessor refuse to restore them, trover,
detinue, or replevin will lie, at the option of the plaintiff.
3.-3. There may also be a detainer of land and this is either lawful
and peaceable, or unlawful and forcible. 1. The detainer is lawful where the
entry has been lawful, and the estate is held by virtue of some right. 2. It
is unlawful and forcible, where the entry has been unlawful, and with force,
and it is retained, by force, against right; or even when the entry has been
peaceable and lawful, if the detainer be by force, and against right; as, if
a tenant at will should detain with force, after the will has determined, he
will be guilty of a forcible detainer. Hawk. P. C. ch. 64, s. 22; 2 Chit.
Pr. 288; Com. Dig, B. 2; 8 Cowen, 216; 1 Hall, 240; 4 John. 198; 4 Bibb,
501. A forcible detainer is a distinct offence from a forcible entry. 8
Cowen, 216. See Forcible entry and detainer.
4.-4. A writ or instrument, issued or made by a competent officer,
authorizing the keeper of a prison to keep in his custody a person therein
named. A detainer may be lodged against. one within the walls of a prison,
on what account soever he is there. Com. Dig. Process, E 3 b.