knee-jerk reaction
nounUK /ˌniː dʒɜːk riˈækʃn/
US /ˌniː dʒɜːrk riˈækʃn/
A quick answer you give without thinking first.
When the teacher asked if I ate the cookie, my knee-jerk reaction was to say no.
RELATED WORDS
OTHER MEANINGS
2. A sudden physical movement of the leg when the knee is tapped.
The doctor tapped my knee and got a knee-jerk reaction.
3. A fast, unplanned response to something surprising or upsetting.
Her knee-jerk reaction to the loud noise was to jump.
4. An immediate opinion formed without careful thought.
His knee-jerk reaction to the new rule was to complain.