has a yellow streak 比较胆怯、不勇敢

如果说某人 has a yellow streak, 那意思就是此人比较胆怯、不勇敢。

例句

We went rock climbing at the weekend. I loved it, but my friend refused to try it. He’s got a real yellow streak.

The public accused the government minister of having a yellow streak after he refused to answer some difficult questions.

请注意

如果一个人 has a mean streak, 那此人会经常做出卑劣、尖酸刻薄的事情。

My boss won't give me a pay rise - he's got a real mean streak.