drop the ball vs blunder

drop the ball is not a noun while blunder is a noun.

Word	Noun	Adjective	Verb	Adverb
drop the ball	No	No	Yes	No
blunder	Yes	No	Yes	No

As verbs, drop the ball and blunder are synonyms defined as:

drop the ball and blunder: commit a faux pas or a fault or make a serious mistake

Other synonyms of drop the ball include boob, goof, sin.

drop the ball (noun)	blunder (noun)
	an embarrassing mistake

drop the ball (verb)	blunder (verb)
commit a faux pas or a fault or make a serious mistake	utter impulsively
	make one's way clumsily or blindly
	commit a faux pas or a fault or make a serious mistake