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]