Definition
A 'balls-up' is a vulgar term for a significant mistake or chaotic situation, similar to a 'foul-up' or 'mess-up'. It implies a major error or mismanagement leading to a considerable problem. This term is considered offensive in many contexts. Think of a situation where everything that could go wrong, did go wrong. Synonymous with 'clusterfuck'. It's generally best to avoid this term in polite company.