obstruction vs rub

obstruction and rub both are nouns.

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

As nouns, rub is a hyponym of obstruction; that is, rub is a word with a more specific, narrower meaning than obstruction:

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

Other hyponyms of obstruction include barrier, roadblock, hang-up, hitch, snag, hurdle, stymie, stymy.

obstruction (noun)	rub (noun)
getting in someone's way	the act of rubbing or wiping
the act of obstructing	an unforeseen obstacle
any structure that makes progress difficult
something immaterial that stands in the way and must be circumvented or surmounted
the physical condition of blocking or filling a passage with an obstruction

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