DEPOSIT INSURANCE: A program of guaranteeing, or insuring, customers' deposits at a bank or similar institution. Since the 1930s bank deposits have been insured by the Federal Deposit Insurance Corporation (FDIC). Other programs have insured deposits at credit unions and savings and loan associations. The FDIC works like this -- If a bank is unable to pay back all or part of its customers' deposits because it has done something like go out of business, then the FDIC steps in to make up the difference--up to a pretty hefty limit. See also | bank | Federal Deposit Insurance Corporation | fractional-reserve banking | bank panic | Great Depression | depression | bank reserves |