Definition
to unexpectedly encounter someone familiar
无意间碰见（某人）；不期而遇（某人）
I ran across an old friend at the store.
我在商店里无意间碰到了一位老朋友。
She ran across her classmate on the street.
她在街上无意间碰到了她的同学。
I ran across a former colleague at the library yesterday.
我昨天在图书馆里无意间碰到了一位前同事。