The Collaborative International Dictionary of English v.0.48:

dead beat \dead` beat"\ (d[e^]d`b[=e]t"), deadbeat
\dead"beat`\(d[e^]d"b[=e]t`).
   a loafer, sponger, or swindler; especially, one who does not
   pay his debts. Same as Beat, n., 7. [Low, U.S.]
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Deadbeat \Dead"beat`\, a. (Physics)
   Making a beat without recoil; giving indications by a single
   beat or excursion; -- said of galvanometers and other
   instruments in which the needle or index moves to the extent
   of its deflection and stops with little or no further
   oscillation.
   [1913 Webster]

   Deadbeat escapement. See under Escapement.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Beat \Beat\, n.
   1. A stroke; a blow.
      [1913 Webster]

            He, with a careless beat,
            Struck out the mute creation at a heat. --Dryden.
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   2. A recurring stroke; a throb; a pulsation; as, a beat of
      the heart; the beat of the pulse.
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   3. (Mus.)
      (a) The rise or fall of the hand or foot, marking the
          divisions of time; a division of the measure so
          marked. In the rhythm of music the beat is the unit.
      (b) A transient grace note, struck immediately before the
          one it is intended to ornament.
          [1913 Webster]

   4. (Acoustics & Mus.) A sudden swelling or re["e]nforcement
      of a sound, recurring at regular intervals, and produced
      by the interference of sound waves of slightly different
      periods of vibrations; applied also, by analogy, to other
      kinds of wave motions; the pulsation or throbbing produced
      by the vibrating together of two tones not quite in
      unison. See Beat, v. i., 8.
      [1913 Webster]

   5. A round or course which is frequently gone over; as, a
      watchman's beat; analogously, for newspaper reporters, the
      subject or territory that they are assigned to cover; as,
      the Washington beat.
      [1913 Webster +PJC]

   6. A place of habitual or frequent resort.
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   7. A cheat or swindler of the lowest grade; -- often
      emphasized by dead; as, a dead beat; also, deadbeat.
      [Low]
      [1913 Webster]

   Beat of drum (Mil.), a succession of strokes varied, in
      different ways, for particular purposes, as to regulate a
      march, to call soldiers to their arms or quarters, to
      direct an attack, or retreat, etc.

   Beat of a watch, or Beat of a clock, the stroke or sound
      made by the action of the escapement. A clock is in beat
      or out of beat, according as the stroke is at equal or
      unequal intervals.
      [1913 Webster]

WordNet (r) 3.0 (2006):

deadbeat
    n 1: someone who fails to meet a financial obligation [syn:
         defaulter, deadbeat]