- any party to an incident, case, quarrel, etc., who is incidentally involved.
- (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.
- 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
- providing protection against liability caused by accidental injury or death of other persons or damage to their property
