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knee jerk

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noun
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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Origin of knee jerk

First recorded in 1875–80

Other definitions for knee jerk (2 of 2)

knee-jerk
[ nee-jurk ]
/ ˈniˌdʒɜrk /

adjective
of or relating to a knee-jerk.
Informal. reacting according to a certain habitual manner; unthinking: a knee-jerk liberal.

Origin of knee-jerk

First recorded in 1895–1900
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2021

How to use knee jerk in a sentence

British Dictionary definitions for knee jerk

knee jerk

noun
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
adjective kneejerk
made or occurring as a predictable and automatic response, without thoughtkneejerk 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

Medical definitions for knee jerk

knee jerk

n.
patellar reflex
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.
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