im·plead·er /im-'plē-dər/ n: the act or procedural device of impleading a third party; specif: a petition or complaint brought in a lawsuit by a plaintiff or defendant against a third party who may be liable to that plaintiff or defendant – called also third-party practice; compare counterclaim, cross-claim, interpleader, intervention, joinder
Merriam-Webster’s Dictionary of Law. Merriam-Webster. 1996.