/əˈkyo͞om(y)əˌlādər/
n. 1. Archaic term for a register. On-line use of it as a synonym for register is a fairly reliable indication that the user has been around for quite a while and/or that the architecture under discussion is quite old. The term in full is almost never used of microprocessor registers, for example, though symbolic names for arithmetic registers beginning in A derive from historical use of the term accumulator (and not, actually, from arithmetic). Confusingly, though, an A register name prefix may also stand for address, as for example on the Motorola 680x0 family.
2. A register being used for arithmetic or logic (as opposed to addressing or a loop index), especially one being used to accumulate a sum or count of many items. This use is in context of a particular routine or stretch of code.
"The FOOBAZ routine uses A3 as an accumulator."
3. One's in-basket (esp. among old-timers who might use sense 1).
"You want this reviewed? Sure, just put it in the accumulator."
See stack.