startle reflex vs startle

startle reflex and startle both are nouns.

Word	Noun	Adjective	Verb	Adverb
startle reflex	Yes	No	No	No
startle	Yes	No	Yes	No

As nouns, startle is a hypernym of startle reflex; that is, startle is a word with a broader meaning than startle reflex:

startle reflex: a normal reflex of young infants; a sudden loud noise causes the child to stretch out the arms and flex the legs
startle: a sudden involuntary movement

Other hypernyms of startle reflex include jump, start.

startle reflex (noun)	startle (noun)
a normal reflex of young infants; a sudden loud noise causes the child to stretch out the arms and flex the legs	a sudden involuntary movement

startle reflex (verb)	startle (verb)
	to stimulate to action
	move or jump suddenly, as if in surprise or alarm