rub vs obstacle

rub and obstacle both are nouns.

Word	Noun	Adjective	Verb	Adverb
rub	Yes	No	Yes	No
obstacle	Yes	No	No	No

As nouns, obstacle is a hypernym of rub; that is, obstacle is a word with a broader meaning than rub:

rub: an unforeseen obstacle
obstacle: something immaterial that stands in the way and must be circumvented or surmounted

Other hypernyms of rub include obstruction.

rub (noun)	obstacle (noun)
the act of rubbing or wiping	an obstruction that stands in the way (and must be removed or surmounted or circumvented)
an unforeseen obstacle	something immaterial that stands in the way and must be circumvented or surmounted

rub (verb)	obstacle (verb)
move over something with pressure
cause friction
scrape or rub as if to relieve itching