bulletin board vs bulletin board system

bulletin board and bulletin board system both are nouns.

Word	Noun	Adjective	Verb	Adverb
bulletin board	Yes	No	No	No
bulletin board system	Yes	No	No	No

As nouns, bulletin board and bulletin board system are synonyms defined as:

bulletin board and bulletin board system: a computer that is running software that allows users to leave messages and access information of general interest

Other synonyms of bulletin board include bbs, electronic bulletin board.

bulletin board (noun)	bulletin board system (noun)
a board that hangs on a wall; displays announcements	a computer that is running software that allows users to leave messages and access information of general interest
a computer that is running software that allows users to leave messages and access information of general interest