The Collaborative International Dictionary
Interpleader \In`ter*plead"er\, n.
One who interpleads.
(Law) A proceeding devised to enable a person, of whom the same debt, duty, or thing is claimed adversely by two or more parties, to compel them to litigate the right or title between themselves, and thereby to relieve himself from the suits which they might otherwise bring against him.
Wiktionary
n. 1 (context legal English) One who makes an interplea. 2 (context legal English) Motion for a third party to enter into a lawsuit in process because a matter is being adjudicated in which they have an interest. 3 (context legal English) Process by which a third party asks a court to determine which of two rival claims is to be honored by the third party.
Wikipedia
Interpleader is civil procedure that allows a plaintiff to initiate a lawsuit in order to compel two or more other parties to litigate a dispute. An interpleader action originates when the plaintiff holds property on behalf of another, but does not know to whom the property should be transferred. It is often used to resolve disputes arising under insurance contracts.