third party

American  

noun

1. any party to an incident, case, quarrel, etc., who is incidentally involved.

2. (in a two-party system) a political party formed as a dissenting or independent group from members of one or both of the two prevailing major parties.

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third party British  

noun

1. a person who is involved by chance or only incidentally in a legal proceeding, agreement, or other transaction, esp one against whom a defendant claims indemnity

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adjective

1. insurance providing protection against liability caused by accidental injury or death of other persons or damage to their property

   third-party insurance

Etymology

Origin of third party

An Americanism dating back to 1795–1805

Example Sentences

Neither Party shall disclose, reproduce, disseminate, use, or permit any third party to disclose, reproduce, disseminate, or use any Confidential Information without the prior written consent of the Confiding Party.

From The Wall Street Journal • Apr. 23, 2026

To win an “alienation of affection” claim, as it is known legally, a plaintiff must prove three points: that there was genuine “love and affection” between the spouses before the third party intervened.

From The Wall Street Journal • Apr. 18, 2026

It’s hard to find an eyewitness or reliable third party who can vouch for what took place between people behind closed doors.

From Los Angeles Times • Apr. 17, 2026

“The aim of the measures is to allow third party online search engines, or ‘data beneficiaries’, to optimize their search services and contest Google Search’s position,” the Commission said.

From MarketWatch • Apr. 16, 2026

The third party he presumed responsible was the United States government.

From "Endgame" by Frank Brady

Related Words

• mediator