rugby football vs rugby

rugby football and rugby both are nouns.

Word	Noun	Adjective	Verb	Adverb
rugby football	Yes	No	No	No
rugby	Yes	No	No	No

As nouns, rugby football and rugby are synonyms defined as:

Other synonyms of rugby football include rugger.

rugby football (noun)	rugby (noun)
a form of football played with an oval ball	a form of football played with an oval ball