bulletin vs newsflash

bulletin and newsflash both are nouns.

Word	Noun	Adjective	Verb	Adverb
bulletin	Yes	No	Yes	No
newsflash	Yes	No	No	No

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

bulletin: a brief report (especially an official statement issued for immediate publication or broadcast)
newsflash: a short news announcement concerning some on-going news story

Other hyponyms of bulletin include flash, news bulletin, newsbreak, information bulletin.

bulletin (noun)	newsflash (noun)
a brief report (especially an official statement issued for immediate publication or broadcast)	a short news announcement concerning some on-going news story

bulletin (verb)	newsflash (verb)
make public by bulletin