Definition - What does Detainer mean?
Detainer is when a person illegally withholds an asset or other property from its rightful owner.
In property law, if a landlord evicts a tenant and the tenant does not leave the premises, it would be the subject of a detainer in that the tenant was illegally withholding the landlord's property.
Justipedia explains Detainer
Court injunctions usually get filed when a detainer happens to force the person withholding the property to hand it over to its rightful owners. Criminal convictions can arise as a result of detainers.
Detainer can also refer to a person being held against their will by another person who is not authorized to detain anyone.