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Synonyms

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.

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.
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

"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

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

    kneejerk support
"Collins English Dictionary — Complete & Unabridged" 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Etymology

Origin of knee jerk1

First recorded in 1875–80

Origin of knee-jerk2

First recorded in 1895–1900

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

"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

But a former cabinet minister - strongly opposed to withdrawal - described the idea as "knee jerk nonsense".

From BBC • Aug. 8, 2023

“This is a perfect example of a knee jerk ‘just do something’ mentality,” said Chris McNutt, president of Texas Gun Rights.

From Seattle Times • May 10, 2023

The sell-off was a "knee jerk reaction to an outcome that took a lot of people by surprise," Lotfi Karoui, chief credit strategist at Goldman Sachs, told Reuters.

From Reuters • Mar. 20, 2023

His knee jerk was slighter than on the other side, but it was present and the weakness was due to the loss of power in the muscles.

From Psychotherapy by Walsh, James J. (James Joseph)

Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.