A knee-jerk reaction is what you feel or say at once, from habit, before you have really thought. The picture comes from a doctor’s test: a little tap just below the knee, and your leg kicks out by itself. You do not choose it.

A knee-jerk reaction is what you feel or say at onceKnee-jerk reaction是指你立刻感覺到或說出來的反應，from habit出於習慣，before you have really thought在你真正想過之前。The picture comes from a doctor's test這個畫面來自醫生的一個測試：a little tap just below the knee在膝蓋下面輕輕敲一下，and your leg kicks out by itself你的腳就會自己踢出去。You do not choose it你沒有選擇要不要這樣。

People borrowed that picture for opinions and answers. “A knee-jerk no” means you refused on autopilot. It is often a mild criticism: the speaker thinks you should have paused.

People borrowed that picture for opinions and answers大家把這個畫面借來形容意見和回答。“A knee-jerk no”“A knee-jerk no” means you refused on autopilot意思是你不假思索就拒絕了。It is often a mild criticism這通常是一種溫和的批評：the speaker thinks you should have paused說話的人覺得你應該先停下來想一下。

You will hear it before reaction, response, answer, opposition. As a noun, “a knee-jerk” can mean that automatic reply.

You will hear it你會聽到它 before reaction, response, answer, opposition放在reaction、response、answer、opposition前面。As a noun當名詞用時，“a knee-jerk” can mean that automatic reply“a knee-jerk”可以指那個不假思索的回應。

Though actually, the body reflex is real and useful; the sharp remark is only about the mind being as automatic as the leg. It is informal to neutral, common in news and argument.

Though actually不過其實，the body reflex is real and useful身體的反射動作是真實而且有用的；the sharp remark is only about the mind being as automatic as the leg那句尖銳的批評只是在說腦袋像腳一樣自動反應。It is informal to neutral這個字口語到中性都算，common in news and argument常出現在新聞和爭論裡。