verb · to feel a sense of loss, frustration, or disappointment

由于没能通过面试，他感到非常失落。

verb · referring to something that has disappeared, been forgotten, or no longer exists, especially a civilization or culture

考古学家们致力于寻找那座失落的玛雅古城。

verb · to lose or drop an object

他不小心把钱包失落在公交车上了。