newsflash vs news bulletin

newsflash and news bulletin both are nouns.

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

As nouns, newsflash and news bulletin are synonyms defined as:

newsflash and news bulletin: a short news announcement concerning some on-going news story

Other synonyms of newsflash include flash, newsbreak.

newsflash (noun)	news bulletin (noun)
a short news announcement concerning some on-going news story	a short news announcement concerning some on-going news story