NGA vs federal agency

NGA and federal agency both are nouns.

Word	Noun	Adjective	Verb	Adverb
NGA	Yes	No	No	No
federal agency	Yes	No	No	No

As nouns, federal agency is a hypernym of NGA; that is, federal agency is a word with a broader meaning than NGA:

NGA: a combat support agency that provides geographic intelligence in support of national security
federal agency: an administrative unit of government

Other hypernyms of NGA include agency, authority, bureau, government agency, office.

NGA (noun)	federal agency (noun)
a combat support agency that provides geographic intelligence in support of national security	an administrative unit of government