Third-party
Third-party may refer to any of the following:
1. With a company, a third party is another company with no affiliation or association with the current company. For example, IBM is a third-party company to Computer Hope. Computer Hope supports all third-party computer companies but is not affiliated with any other computer company.
With software, a third-party program is any software, plug-in, or mod that is not included with a program. For example, Norton Anti-Virus is a third-party program for Microsoft Windows since it is not included with Windows.
Finally, with hardware, a third-party hardware upgrade is any upgrade or addition added to an OEM (original equipment manufacturer) computer. For example, if you upgraded a Dell computer with new memory, the memory would be considered third-party hardware.
2. In online games, third party refers to a player attacking another player who's already being attacked by another player or NPC (non-player character). Players often do this because it gives them an advantage in winning the fight because the player is distracted or already hurt.