Definition (出现)
to manifest or occur, particularly in an abrupt or unforeseen manner
突然出现
While browsing the web casually, many ads popped up suddenly.
在随意浏览网页时，许多广告突然弹出。
During the meeting, a new issue popped up unexpectedly in the discussion.
在会议期间，讨论中意外出现了一个新问题。
Their old classmate popped up at the party unexpectedly, surprising everyone.
他们的老同学意外出现在派对上，让每个人都大吃一惊。