news bulletin vs newsbreak

news bulletin and newsbreak both are nouns.

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

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

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

Other synonyms of news bulletin include flash, newsflash.

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