overdraft. 1. A withdrawal of money from a bank in excess of the balance on deposit. [Cases: Banks and Banking  150. C.J.S. Banks and Banking §§ 349–352, 358.] 2. The amount of money so withdrawn. — Abbr. OD; o/d. 3. A line of credit extended by a bank to a customer (esp. an established or institutional customer) who might overdraw on an account.

[Blacks Law 8th]