Greenwich Time vs GMT

Greenwich Time and GMT both are nouns.

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

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

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

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

Greenwich Time (noun)	GMT (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