bbs vs bulletin board system

bbs and bulletin board system both are nouns.

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

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

bbs 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 bbs include bulletin board, electronic bulletin board.

bbs (noun)	bulletin board system (noun)
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