Idiom: Knee Jerk Reaction Posted on 17th May 201816th May 2018 by DoubleClick Knee Jerk Reaction: a quick and automatic reaction without considering carefully Example: Their response was ‘NO’ without considering, even thinking; it was a knee-jerk reaction. Share this:Click to share on Twitter (Opens in new window)Click to share on Facebook (Opens in new window) Related Posted in Idiom and tagged Idiom K.