The Collaborative International Dictionary
balls-up \balls-up\ n. something badly botched or muddled; a foul-up. [British]
Syn: ballup, cockup, mess-up, foul-up.
Wiktionary
n. (context idiomatic British vulgar English) something which becomes muddled or botched in some way.
WordNet
Usage examples of "balls-up".
Mullett was all ready to give me the tin-tack in appreciation of a couple of my more spectacular balls-ups when I had my little moment of triumph.
All the stuff with the red dressinggowns and the sleigh bells is comparatively recent, the result of one of the biggest balls-ups in theological history.
You made a balls-up of your experiments, a few bats died, and if your theories became known outside this Research Centre half the population would be panicking.
I had to make sure that Jack Edgecombe didn't make a balls-up of the farm.