Knee-jerk (adjective)

1. A reaction or response that is automatic and unthinking.
2. A response that is made without considering the situation or facts.

Origin:

From the reflexive motion of the knee, where a tap to the knee will cause it to quickly extend.

Examples:

1. His knee-jerk reaction was to quit his job after the argument with his boss.
2. The politician's knee-jerk response to the crisis was to call for more laws and regulations.
3. The new policy was criticized as being a knee-jerk solution to a complex problem.
4. She had a knee-jerk dislike of anything that was new and unfamiliar.
5. The knee-jerk reaction of the public was to blame the government for the disaster.