What is an accumulator?

In computers an accumulator is a dedicated single purpose register in which arithmetic operations are performed. They cannot be used for addressing memory or any other purpose than arithmetic.

Different computers have different quantities of accumulators, from none to a few dozen depending on the architecture.

An accumulator is someone who, or something which, accumulates, a wet-cell storage battery, or a collective bet on successive events, with both stake and winnings being carried forward to the next bet.