The Collaborative International Dictionary of English v.0.48:

Overdraft \O"ver*draft`\, n. (Banking)
   The act of overdrawing; a draft in excess of the credit
   balance; also, the amount or sum overdrawn.
   [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

overdraft
    n 1: a draft in excess of the credit balance

Moby Thesaurus II by Grady Ward, 1.0:

21 Moby Thesaurus words for "overdraft":
   arrear, arrearage, arrears, back debts, back payments, bankruptcy,
   bouncing check, bust, collapse, crash, default, deferred payments,
   deficit, deficit financing, dollar gap, failure, insolvency,
   insufficient funds, kited check, overdrawn account, receivership