third par·ty • n. a person or group besides the two primarily involved in a situation, esp. a dispute. ∎ a political party organized as an alternative to the major parties in a two-party system. • adj. of or relating to a person or group besides the two primarily involved in a situation: third-party suppliers.
A generic legal term for any individual who does not have a direct connection with a legal transaction but who might be affected by it.
A third-party beneficiary is an individual for whose benefit a contract is created even though that person is a stranger to both the agreement and the consideration. Such an individual can usually bring suit to enforce the contract or promise made for his or her benefit.
A third-party action is another name for the procedural device of impleader, which is used in a civil action by a defendant who wants to bring a third party into a lawsuit because that party will ultimately be liable for all, or part of, the damages that may be awarded to the plaintiff.