Andrew M. Greeley 
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Around 1876, the sudden involuntary extension of the leg in response to a light blow just below the knee, which is also known as the patellar reflex, was given the refreshingly simple designation knee jerk. In the 1950s, knee-jerk became an adjective with a figurative sense that doesn't require any actual twitching. "As a salesman, I'm getting a bit weary of the knee-jerk association of a con artist with my professional calling," a correspondent once wrote to The New York Times Magazine. Knee-jerk often has a negative connotation. It usually denotes a too-hasty, impulsive, perhaps even irrational response that is often based on preconceived notions.
Examples of knee-jerk in a Sentence
Literary Hub, 12 Mar. 2026
Tuesday was defined by the knee-jerk reactions to multiple — and often conflicting — headlines about the status of the Iran war and the ability for oil tankers to pass through the Strait of Hormuz.
—Jeff Marks, CNBC, 11 Mar. 2026
Mark Faithfull, Forbes.com, 29 Aug. 2025
Flynn’s suggestion to move the rowdy Southie parade downtown is a knee jerk reaction to appease the upscale yuppie families and other residents who have taken over the traditional working class Irish American neighborhood.
—Joe Battenfeld, Boston Herald, 21 Mar. 2024
See All Example Sentences for knee-jerk
Cite this Entry
“Knee-jerk.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/knee-jerk. Accessed 16 Mar. 2026.
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