noun an error, a mistake. A number of etymologies have been suggested, among them: bookkeeping amendments written at a tilt, and the 'cock' (spigot) of ale-barrels; while it is possible that the origins lurk in such innocence it is certain that modern usage is influenced by 'fuck-up', 'balls-up', etc., which presumes 'cock' is a 'penis' UK, 1948.► couldn't organise a cock-up in a brothelused of an inefficient person. A later variation of COULDN'T ORGANISE A FUCK IN A BROTHEL with a neat pun on COCK-UP (an error) and COCK (the penis) UK, 2001