The Collaborative International Dictionary of English v.0.48:

Debit \Deb"it\, n. [L. debitum what is due, debt, from debere to
   owe: cf. F. d['e]bit. See Debt.]
   A debt; an entry on the debtor (Dr.) side of an account; --
   mostly used adjectively; as, the debit side of an account.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Debit \Deb"it\, v. t. [imp. & p. p. Debited; p. pr. & vb. n.
   Debiting.]
   1. To charge with debt; -- the opposite of, and correlative
      to, credit; as, to debit a purchaser for the goods sold.
      [1913 Webster]

   2. (Bookkeeping) To enter on the debtor (Dr.) side of an
      account; as, to debit the amount of goods sold.
      [1913 Webster]

WordNet (r) 3.0 (2006):

debit
    n 1: an accounting entry acknowledging sums that are owing [syn:
         debit, debit entry] [ant: credit, credit entry]
    v 1: enter as debit [ant: credit]

Moby Thesaurus II by Grady Ward, 1.0:

67 Moby Thesaurus words for "debit":
   balance, balance the books, bereavement, book, budgeting,
   capitalize, carry, carry over, cast up accounts, charge off,
   close out, close the books, cost, costing, costing-out, credit,
   damage, dead loss, debiting, deficit spending, denial, denudation,
   deprivation, despoilment, destruction, detriment, disbursal,
   disbursement, dispossession, divestment, docket, double entry,
   enter, entry, expenditure, expense, forfeit, forfeiture, injury,
   item, journalize, keep books, log, loser, losing, losing streak,
   loss, make an entry, minute, notation, note, payment, perdition,
   post, post up, privation, robbery, ruin, sacrifice, scheduling,
   single entry, spending, spoliation, strike a balance, stripping,
   taking away, total loss



Bouvier's Law Dictionary, Revised 6th Ed (1856):

DEBIT, accounts, commerce. A term used in bookkeeping, to express the left-
hand page of the ledger, to which are carried all the articles supplied or
paid on the subject of an account, or that are charged to that account. It
also signifies the balance of an account.