great deal vs mess

great deal and mess both are nouns.

Word	Noun	Adjective	Verb	Adverb
great deal	Yes	No	No	No
mess	Yes	No	Yes	No

As nouns, great deal and mess are synonyms defined as:

great deal and mess: (often followed by `of') a large number or amount or extent

great deal (noun)	mess (noun)
(often followed by `of') a large number or amount or extent	a (large) military dining room where service personnel eat or relax
	a meal eaten in a mess hall by service personnel
	soft semiliquid food
	(often followed by `of') a large number or amount or extent
	a state of confusion and disorderliness
	informal terms for a difficult situation

great deal (verb)	mess (verb)
	make a mess of or create disorder in
	eat in a mess hall