An automatic reaction refers to a response or action that occurs spontaneously and without conscious thought or effort. There are various synonyms that can be used interchangeably with the phrase automatic reaction, such as reflex, instinct, and innate response. A reflex is an involuntary action that is triggered by a particular stimulus, such as a knee-jerk reaction. Similarly, an instinct is an innate, natural behavior that is triggered by specific environmental conditions. Other synonyms for automatic reaction include habitual response, programmed behavior, and unconscious action. Regardless of the terminology used, an automatic reaction is an essential aspect of human behavior that helps individuals respond quickly to stimuli and adapt to changing situations.