wattmeter

from WordNet (r) 3.0 (2006)

wattmeter
    n 1: an instrument for measuring in watts the flow of power in
         an electrical circuit

from The Collaborative International Dictionary of English v.0.48

Wattmeter \Watt"me`ter\, n. [Watt + meter.] (Physics)
   An instrument for measuring power in watts, -- much used in
   measuring the energy of an electric current.
   [1913 Webster]