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• knee jerk
  knee jerk

  noun

  a reflex extension of the leg, caused by contraction of the quadriceps, resulting from a sharp tap on the patellar tendon; patellar reflex.
• knee-jerk
  knee-jerk

  adjective

  of or relating to a knee-jerk.

knee jerk

¹ American  

noun

1. a reflex extension of the leg, caused by contraction of the quadriceps, resulting from a sharp tap on the patellar tendon; patellar reflex.

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knee-jerk ² American  

[nee-jurk] / ˈniˌdʒɜrk /

adjective

1. of or relating to a knee-jerk.

2. Informal. reacting according to a certain habitual manner; unthinking.

   a knee-jerk liberal.

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knee jerk British  

noun

1. Also called: patellar reflex.  physiol an outward reflex kick of the lower leg caused by a sharp tap on the quadriceps tendon just below the patella

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1. made or occurring as a predictable and automatic response, without thought

   kneejerk support

Etymology

Origin of knee jerk¹

First recorded in 1875–80

Origin of knee-jerk²

First recorded in 1895–1900

Example Sentences

"Everyone recognizes there is a growing antibiotic resistance crisis, and the knee jerk reaction is to develop new antibiotics," You added.

From Science Daily • Feb. 22, 2024

Unite's deputy regional secretary, Davy Thompson, said minimum service levels are "the most invidious example of knee jerk legislating this country has seen in a long time".

From BBC • Jan. 13, 2024

"So we did have that sort of knee jerk over-reaction and it is something we have seen repeatedly in recent years here, sort of this triumph of hope over experience that markets keep going through."

From Reuters • Sep. 12, 2023

“I feel changing it because of criminal activity is a knee jerk rection and it’s not going to change anything,” she said last week.

From Seattle Times • Mar. 24, 2022

The loss of the knee jerk is always observed in time.

From Mother's Remedies Over One Thousand Tried and Tested Remedies from Mothers of the United States and Canada by Ritter, Thomas Jefferson