cosmic microwave background vs CMB

cosmic microwave background and CMB both are nouns.

Word	Noun	Adjective	Verb	Adverb
cosmic microwave background	Yes	No	No	No
CMB	Yes	No	No	No

As nouns, cosmic microwave background and CMB are synonyms defined as:

cosmic microwave background and CMB: (cosmology) the cooled remnant of the hot big bang that fills the entire universe and can be observed today with an average temperature of about 2.725 kelvin

Other synonyms of cosmic microwave background include CBR, CMBR, cosmic background radiation, cosmic microwave background radiation.

cosmic microwave background (noun)	CMB (noun)
(cosmology) the cooled remnant of the hot big bang that fills the entire universe and can be observed today with an average temperature of about 2.725 kelvin	(cosmology) the cooled remnant of the hot big bang that fills the entire universe and can be observed today with an average temperature of about 2.725 kelvin