Reflex refers to an innate, unlearned, consistent, automatic response to a stimulus; a mechanism that enables a specific environmental event to elicit a specific response. Example of a reflex is an eyeblink.
Moreover, Reflex is a natural, simple, involuntary motor reaction or response to an external stimulus that causes a physical response. Also an unlearned response induced by specific stimuli that have biological relevance to the organism.
Other /More definition:
Reflex refers to an involuntary motor response to a simple stimulus. It is an unlearned, stereotypical response to a stimulus
Lexicon of Psychology - Terms, Treatments, Biographies,