The Collaborative International Dictionary of English v.0.48:

Debit card \Deb"it card`\, n. [See debit.]
   a small usually plastic card with a magnetic coded number,
   similar to a credit card, which is used to pay for purchases
   by the electronic deduction of a sum of money (a debit)
   directly from the card-holder's bank account. Such cards do
   not require the establishment of a credit line, and such
   transactions do not incur any interest payments.
   [1913 Webster]

WordNet (r) 3.0 (2006):

debit card
    n 1: a card (usually plastic) that enables the holder to
         withdraw money or to have the cost of purchases charged
         directly to the holder's bank account