third party

Pronunciation

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Noun

third party (countable and uncountable, plural third parties)

1. Someone not directly involved in a transaction. A third entity in the Seller (first party) and Customer (second party) relationship. A Seller may employ a third party to perform specific services to augment the value of a product. For example, a manufacturer may employ a third party to pack and distribute a product. A computer manufacturer may augment their product with software from a third-party supplier.
2. Someone only incidentally or tangentially connected to an incident or dispute; someone other than the principals; a bystander or independent witness.
3. A political party in opposition to the main parties in a two-party system
   • 2010, Duncan Watts, Dictionary of American Government and Politics, →ISBN, page 177:

     Those who belong to the Libertarian Party serve a much larger pro-liberty community and have the specific mission of electing libertarians to public office. They traditionally billed themselves as 'America's largest third party'.