great deal vs flock

great deal and flock both are nouns.

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

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

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

great deal (noun)	flock (noun)
(often followed by `of') a large number or amount or extent	a group of birds
	a group of sheep or goats
	a church congregation guided by a pastor
	an orderly crowd
	(often followed by `of') a large number or amount or extent

great deal (verb)	flock (verb)
	come together as in a cluster or flock
	move as a crowd or in a group