third-party software used to cheat or gain an unfair advantage in online games

他在网络游戏里因为开外挂被封号了。

attached externally (e.g. equipment or fuel tank)

这架战斗机携带了两个外挂副油箱。

verb · a software component or add-on that adds a specific feature to an existing computer program

这个浏览器支持多种实用的功能外挂。