sneezing vs reflex action

sneezing and reflex action both are nouns.

Word	Noun	Adjective	Verb	Adverb
sneezing	Yes	No	No	No
reflex action	Yes	No	No	No

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

sneezing: a symptom consisting of the involuntary expulsion of air from the nose
reflex action: an automatic instinctive unlearned reaction to a stimulus

sneezing (noun)	reflex action (noun)
a symptom consisting of the involuntary expulsion of air from the nose	an automatic instinctive unlearned reaction to a stimulus