GMT vs Greenwich Mean Time

GMT and Greenwich Mean Time both are nouns.

Word	Noun	Adjective	Verb	Adverb
GMT	Yes	No	No	No
Greenwich Mean Time	Yes	No	No	No

As nouns, GMT and Greenwich Mean Time are synonyms defined as:

GMT and Greenwich Mean Time: the local time at the 0 meridian passing through Greenwich, England; it is the same everywhere

Other synonyms of GMT include Greenwich Time, universal time, UT1, UT.

GMT (noun)	Greenwich Mean Time (noun)
the local time at the 0 meridian passing through Greenwich, England; it is the same everywhere	the local time at the 0 meridian passing through Greenwich, England; it is the same everywhere