I waited my chance and slipped out when no one was looking.

我等待时机，趁没人注意时溜了出去。

《牛津词典》

She'd promised to give him driving lessons, on the quiet, when no one could see.

她答应在无人看见时秘密地给他上驾驶课。

《柯林斯英汉双解大词典》

Look back on those days when you were the little child, how many times did you try when no one was watching, or when no one was cheering?

回想一下你小时候的那些日子，在没有人观看或没有人欢呼的时候，你试了多少次？

youdao

That means they're prone to intervene and take positive action when no one else will.

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The Mexican players were livid when no penalty was called, surrounding Guatemalan referee Walter Lopez.

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