knee-jerk (adjective) – (of a response) automatic and unthinking

(Pronounced nee-jerk)

To remember the definition of the word knee-jerk, use the following mnemonic:

She kneed the jerk (knee-jerk) in the face. It was an automatic response to his insult. 

Examples of knee-jerk (adjective) in a sentence

Her knee-jerk reaction to the argument got her into a lot of trouble. 

His knee-jerk response to the situation was far more relaxed than they had expected.

He was a frugal man who had a knee-jerk reaction to the mere thought of spending money.