stumble vs blunder

stumble and blunder both are nouns.

Word	Noun	Adjective	Verb	Adverb
stumble	Yes	No	Yes	No
blunder	Yes	No	Yes	No

As nouns, blunder is a hypernym of stumble; that is, blunder is a word with a broader meaning than stumble:

Other hypernyms of stumble include bloomer, blooper, boner, boo-boo, botch, bungle, flub, foul-up, fuckup, pratfall.

stumble (noun)	blunder (noun)
an unsteady uneven gait	an embarrassing mistake
an unintentional but embarrassing blunder

stumble (verb)	blunder (verb)
make an error	utter impulsively
miss a step and fall or nearly fall	make one's way clumsily or blindly
walk unsteadily, tripping repeatedly	commit a faux pas or a fault or make a serious mistake
encounter by chance