The Collaborative International Dictionary of English v.0.48:

oscillograph \oscillograph\ n.
   1. a device for making a record of the wave forms of
      fluctuating .
      [WordNet 1.5]

The Collaborative International Dictionary of English v.0.48:

Oscillograph \Os"cil*lo*graph\, n. [L. oscillare to swing +
   -graph.] (Elec.)
   An apparatus for recording or indicating alternating-current
   wave forms or other electrical oscillations, especially of
   voltages or currents; it usually consists of a galvanometer
   with strong field, in which the mass of the moving part is
   very small and frequency of vibration very high. --
   Os`cil*lo*graph"ic, a.
   [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

oscillograph
    n 1: a device for making a record of the wave forms of
         fluctuating voltages or currents