newsbreak vs news bulletin

newsbreak and news bulletin both are nouns.

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

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

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

Other synonyms of newsbreak include flash, newsflash.

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