by a hair's breadth差一點；死裡逃生。breadth是幅度的意思，從字面上看by a hair's breadth是比喻僅有一根頭髮的距離，用來形容極其驚險，幹鈞一發。特別僥倖的情況和心情也可以用within a hair's breadth描述。
看看老外聊天時怎麼用by a hair's breadth：
Julie: I thought we were going to miss the flight!
Kevin: We are so lucky to have made it by a hair's breadth.
Julie: Thanks to the taxi driver. He took a shortcut for us.
Kevin: Hope we didn't get him any ticket.
Julie: Yeah, he ran two red lights on the way.
朱莉：我以為我們趕不上這趟航班了！
凱文：我們能千鈞一髮地趕上實在太幸運了。
朱莉：多虧了計程車司機，他為我們抄了近路。
凱文：希望我們沒害他被開罰單。
朱莉：是啊，他一路上闖了兩個紅燈。
by a hair's breadth例句精選：
We won by a hair's breadth.
我們以些微之差贏了對手。
He escaped the danger by a hair's breadth.
他這回真是九死一生。
Linda：Did you see the news about the huge car accident？
Bob：Actually，I was there.I missed it by a hair's breadth.
琳達：你看了那場大車禍的新聞報導了嗎？
鮑勃：其實我就在現場，差一點就無法脫身了。
拓展學習：
incidental 偶然的；意料之外的
coincidence 巧合
thrilling 毛骨悚然的
by a fluke 僥倖
climb the walls 極為焦慮；緊張擔憂
play it by ear 隨機應變