Overdraft

n. overdrawing of a bank account; amount overdrawn; limit to which money may be withdrawn from the bank on credit; draft of air flowing over a fire (e.g. in a furnace)

An overdraft occurs when withdrawals from a bank account exceed the available balance which gives the account a negative balance - a person can be said to have gone "overdrawn".If there is a prior agreement with the account provider for an overdraft protection plan, and the amount overdrawn is within this authorised overdraft, then interest is normally charged at the agreed rate. If the balance exceeds the agreed terms, then fees may be charged and higher interest rate might apply.
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Noun
1. a draft in excess of the credit balance
(hypernym) draft, bill of exchange, order of payment

Provision of instant credit by a lending institution.