An accumulator bet, or acca, is a bet that combines four or more selections. If there are four selections it is sometimes also known as a four-fold accumulator, or for five selections, a five-fold, and so on. The more parts to the bet the greater the potential return as the odds are multiplied and the proceeds of each winning bet rolls over to the next. The downside is that one losing bet upends the entire bet. Accumulators can be rather speculative in nature, but there are a great many examples online of huge odds football and horse racing acca wins over the years.