Definitions
1.NounSomeone 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.NounSomeone only incidentally or tangentially connected to an incident or dispute; someone other than the principals; a bystander or independent witness.
3.NounA political party in opposition to the main parties in a two-party system.
4.NounA person or party not directly involved with an arrangement, in contrast to active parties, characteristically the first party (producer) and second party (consumer).