reflex

(noun) an automatic instinctive unlearned reaction to a stimulus. Synonyms: reflex response, reflex action, instinctive reflex, innate reflex, inborn reflex, unconditioned reflex, physiological reaction.

(adj) without volition or conscious control. Synonyms: automatic, reflex(prenominal), reflexive. Examples: "The automatic shrinking of the pupils of the eye in strong light." "A reflex knee jerk." "Sneezing is reflexive."