- 1反射性的、不假思索的（延伸義）；膝反射（醫學本義）
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. People borrowed that picture for opinions and answers. “A knee-jerk no” means you refused on . It is often a mild criticism: the speaker thinks you should have paused. You will hear it before reaction, response, answer, opposition. As a noun, “a knee-jerk” can mean that automatic reply. 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.
From the word’s history
Compound of knee + jerk, a figurative use of the patellar reflex; first attested c. 1876.
knee 加 jerk，比喻膝跳反射，約 1876 年起見於文獻。
組成knee + jerk. First used around 1876, from the kick you cannot stop when a doctor taps below the knee.
原始詞典資料2 筆記錄
以下是外部詞典記錄的用法，摘錄並精簡格式，我們還沒有寫成教學內容。上面的說明才是我們自己寫的；有些用法可能上面已經講過了。
knee-jerkadj
- 1
Unthinking, not carefully considered, (nearly) automatic, spontaneous, easily predictable.
- He gave a knee-jerk response.
- There were knee-jerk demands from trade unions for immediate withdrawal of all HSTs; these were wrong-headed.
knee-jerknoun
- 1
A sudden reflexive movement of the leg below the knee, as a reaction to a tap to the tendon just below the patella (kneecap).
摘錄自 英文維基詞典 English Wiktionary，已精簡格式；依 CC BY-SA 4.0 授權使用，改動後的內容同樣以此授權提供。