过眼云烟的英文：
as transient and ephemeral as a fleeting cloud

参考例句：

That haunting episode of bygone days was to her mother but a passing accident.
那件日夜盘据在她心头的住事，对于她母亲不过是一件过眼云烟的偶然事件罢了。

But also a warning against overrating the passing glories of wealth, power and great good fortune.
这句话同时也警示我们，财富、权力或鸿运当头的荣耀，都不过是过眼云烟，我们不必太放在心上。

transient是什么意思：
a.【正式】
1.暂短的；转瞬即逝的；倏忽
2.暂住的；过往的；临时的
n.【美】暂住某地的人；过往旅客；临时工

step function transient response
阶跃函数瞬态特性

We are just the transients at the hotel.
我们只是旅馆里的过往旅客。

Transient area is a storage area used for transient programs of routines.
暂驻存储区是用来临时存放暂态程序或例行程序的一种储区。

ephemeral是什么意思：
adj. 短暂的；朝生暮死的

It is not something ephemeral.
它不是朝生暮死的东西。

Her success as a singer was ephemeral.
作为歌唱家她取得的成功只是昙花一现。

Such novels came forward to enjoy ephemeral popularity only.
这样的小说只是昙花一现的东西而已。

fleeting是什么意思：
adj. 稍纵即逝的，短暂的

That is a fleet horse.
那是一匹快马。

This is a vain and fleeting thing.
这是一种空虚的、转瞬即逝的东西。

The world is like a fleeting show.
人世如白驹过隙。