"Flub" as a word can serve as both noun and verb; the action being to mess up or botch, and the noun being the mistake or botching in question.
The word has an unknown origin, but is similar in form to other words indicating a mistake: flop, foul, fumble, and fluff all mean pretty much the same thing in the given context.
The word was appropriated for the 1960 Disney film The Absent-Minded Professor, when the titular character created a new goo on accident that turned out to provide a surprise spring in one's step. Combining "flub" and "rubber", the concoction was named Flubber.