play something by ear 

play something by ear就是想做一件事，可是又不能確定是否可能，只好到時(shí)候看情況再說(shuō)，就像中文里說(shuō)的'看情況而定'!

I didn't have time to prepare for the job interview. I will have to play it by ear.

我沒(méi)時(shí)間為面試做準(zhǔn)備，只好見(jiàn)機(jī)行事了。

A: 'Are we meeting at noon on Saturday?'

我們周六中午見(jiàn)好嗎?

B: 'I have to run some errands in the morning, so let's play it by ear.'

我早上要辦點(diǎn)事，所以我們到時(shí)候看情況再說(shuō)吧。