newsflash vs bulletin

newsflash and bulletin both are nouns.

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

As nouns, bulletin is a hypernym of newsflash; that is, bulletin is a word with a broader meaning than newsflash:

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

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

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