stumble across/on/upon something/somebody
to discover something/somebody unexpectedly 意外发现;偶然遇见
Police have stumbled across a huge drugs ring. 警方无意中发现一个庞大的贩毒集团。
standby:a person or thing that can always be used if needed, for example if somebody/something else is not available or if there is an emergency 后备人员;备用物品
I always keep a pizza in the freezer as a standby. 我总会在冰箱里放一个比萨饼应急。
a standby electricity generator 备用发电机
