CPU vs central processing unit

CPU and central processing unit both are nouns.

Word	Noun	Adjective	Verb	Adverb
CPU	Yes	No	No	No
central processing unit	Yes	No	No	No

As nouns, CPU and central processing unit are synonyms defined as:

CPU and central processing unit: (computer science) the part of a computer (a microprocessor chip) that does most of the data processing

Other synonyms of CPU include C.P.U., central processor, mainframe, processor.

CPU (noun)	central processing unit (noun)
(computer science) the part of a computer (a microprocessor chip) that does most of the data processing	(computer science) the part of a computer (a microprocessor chip) that does most of the data processing