USMC vs United States Marine Corps

USMC and United States Marine Corps both are nouns.

Word	Noun	Adjective	Verb	Adverb
USMC	Yes	No	No	No
United States Marine Corps	Yes	No	No	No

As nouns, USMC and United States Marine Corps are synonyms defined as:

USMC and United States Marine Corps: an amphibious division of the United States Navy

Other synonyms of USMC include Marine Corps, Marines, United States Marines, US Marine Corps.

USMC (noun)	United States Marine Corps (noun)
an amphibious division of the United States Navy	an amphibious division of the United States Navy