shiver vs unconditioned reflex

shiver and unconditioned reflex both are nouns.

Word	Noun	Adjective	Verb	Adverb
shiver	Yes	No	Yes	No
unconditioned reflex	Yes	No	No	No

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

shiver: a reflex motion caused by cold or fear or excitement
unconditioned reflex: an automatic instinctive unlearned reaction to a stimulus

shiver (noun)	unconditioned reflex (noun)
a reflex motion caused by cold or fear or excitement	an automatic instinctive unlearned reaction to a stimulus
an almost pleasurable sensation of fright

shiver (verb)	unconditioned reflex (verb)
shake, as from cold
tremble convulsively, as from fear or excitement