His mouth tightened into a thin line.

他的嘴抿成了一道细缝。

《牛津词典》

Her lips compressed into a thin line.

她的双唇抿成了一道缝。

《牛津词典》

Her stare was malevolent, her mouth a thin line.

她目光狠毒，嘴唇紧闭。

《柯林斯英汉双解大词典》

It was a place where the line between reality and unreality is extremely thin.

VOA: special.2010.10.31

There's a very thin line between the two and we therefore use the same pedagogical methods in the sense that we've got to do the following.

两者之间的差别很微妙,因此我们接下来要做的,就是采用与语言课相同方法教学

耶鲁公开课 - 聆听音乐课程节选

"Our margins are really thin, in terms of our bottom line, and any additional costs have to be absorbed by the farmer because we can't pass on those costs to consumers directly,"

VOA: standard.2009.12.12

James McConville gestures toward a valley far below, and a thin line of asphalt.

NPR: Commanders Look For New Strategy In Afghanistan

Still, that Seahawks-Falcons game was a classic, and shows the thin line quarterbacks and coaches tread.

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He wouldn't go along with cheating or with blurring that thin line 'tween right and wrong.

NPR: Baseball, Apple Pie and Steroids