stumble vs flub

stumble and flub both are nouns.

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

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

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

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

stumble (verb)	flub (verb)
make an error	make a mess of, destroy or ruin
miss a step and fall or nearly fall
walk unsteadily, tripping repeatedly
encounter by chance