foreign terrorist organization vs RPA-ABB

foreign terrorist organization and RPA-ABB both are nouns.

Word	Noun	Adjective	Verb	Adverb
foreign terrorist organization	Yes	No	No	No
RPA-ABB	Yes	No	No	No

foreign terrorist organization (noun)	RPA-ABB (noun)
a political movement that uses terror as a weapon to achieve its goals	an urban hit squad and guerrilla group of the Communist Party in the Philippines; formed in the 1980s