NOUN (3)

1. the state of owing something (especially money);
- Example: "he is badly in debt"

2. money or goods or services owed by one person to another;

3. an obligation to pay or do something;

The Collaborative International Dictionary of English v.0.48:

Debt \Debt\, n. [OE. dette, F. dette, LL. debita, fr. L. debitus
   owed, p. p. of debere to owe, prop., to have on loan; de- +
   habere to have. See Habit, and cf. Debit, Due.]
   1. That which is due from one person to another, whether
      money, goods, or services; that which one person is bound
      to pay to another, or to perform for his benefit; thing
      owed; obligation; liability.
      [1913 Webster]

            Your son, my lord, has paid a soldier's debt.
                                                  --Shak.
      [1913 Webster]

            When you run in debt, you give to another power over
            your liberty.                         --Franklin.
      [1913 Webster]

   2. A duty neglected or violated; a fault; a sin; a trespass.
      "Forgive us our debts." --Matt. vi. 12.
      [1913 Webster]

   3. (Law) An action at law to recover a certain specified sum
      of money alleged to be due. --Burrill.
      [1913 Webster]

   Bond debt, Book debt, etc. See under Bond, Book, etc.


   Debt of nature, death.
      [1913 Webster]

WordNet (r) 3.0 (2006):

debt
    n 1: the state of owing something (especially money); "he is
         badly in debt"
    2: money or goods or services owed by one person to another
    3: an obligation to pay or do something

The Devil's Dictionary (1881-1906):

DEBT, n.  An ingenious substitute for the chain and whip of the slave-
driver.

    As, pent in an aquarium, the troutlet
    Swims round and round his tank to find an outlet,
    Pressing his nose against the glass that holds him,
    Nor ever sees the prison that enfolds him;
    So the poor debtor, seeing naught around him,
    Yet feels the narrow limits that impound him,
    Grieves at his debt and studies to evade it,
    And finds at last he might as well have paid it.
                                                        Barlow S. Vode