We must not let our youth slip idly by.

我们不能让青春虚度。

《新英汉大辞典》

It eats in her to stand idly by.

站在一旁无所事事，这使她很不好受。

youdao

Thankfully, the world is not standing idly by.

值得庆幸的是，全世界并没有惊慌失措。

youdao

"We will not stand idly by as North Korea builds the capability to wreak destruction on any target in the region or on us.

VOA: standard.2009.05.30

Those who seek peace cannot stand idly by as nations arm themselves for nuclear war.

CNN: Obama: 'Peace requires responsibility'

Will Senator Durbin's colleagues sit idly by as he contributes to such a wholly unacceptable outcome?

CENTERFORSECURITYPOLICY: Durbin launches the 'anti-Pete King' hearing

Were it to do so, Bulgaria, Greece and Turkey would not feel able to stand idly by.

ECONOMIST: Don��t let the endgame be his