define a reflex
A reflex action, differently known as a reflex, is an involuntary and nearly instantaneous movement in response to a stimulus.Scientific use of the term reflex refers to a behavior that is mediated via the reflex arc; this does not apply to casual uses of the term reflex.cientific use of the term reflex refers to a behavior that is mediated via the reflex arc; this does not apply to casual uses of the term reflex.