Nickname for a kind of fraud or confidence game, more specifically, a kind of bill fraud.
An insider arranges for all of the fractional cents (e.g. from periodic interest payments) to be funnelled into a single account.
In this way, each transaction has only a thin slice removed (much like the slicing of a salami), but the accrued balance of the dump account (depending on the size of the institution in question) eventually grows big enough to clean out and clear out.
This scam figured prominently in the plotline of the film Superman III, as well as Office Space.