third party

noun third parties · 3rd party · 3d party

1. Someone not directly involved in a transaction; an entity beyond the seller (first party) and customer (second party). A seller may employ a third party to perform specific services to augment the value of a product, such as packing and distribution.
2. Someone only incidentally or tangentially connected to an incident or dispute; someone other than the principals; a bystander or independent witness.
3. US A political party in opposition to the main parties in a two-party system. 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'.
4. A person or party not directly involved with an arrangement, in contrast to active parties, characteristically the first party (producer) and second party (consumer).