Third Party Definition: A person who is not privy to a contract or a party in a lawsuit. In Apex, Justice Brooker adopted these words: "The term third party is generally understood to mean any party that is not a party to a contract .... "A person who is not a party to a lawsuit, agreement, or other transaction but who is usually somehow implicated in it; someone other than the principal parties." In the context of contract law, a third party is one who does not have privity of contract with other persons to a contract. REFERENCES: Apex Corporation v. Ceco Developments 2005 ABQB 656 Duhaime, Lloyd, Legal Definition of Third Party Claim Categories & Topics: Civil Litigation & Evidence Law Dictionary Contract Law Dictionary Find you are constantly looking up definitions? Try our search provider (works in most modern browsers) If you find an error or omission in Duhaime's Legal Dictionary, or if you have legal term suggestion, we'd love to hear from you!