The Collaborative International Dictionary of English v.0.48:

oscilloscope \os*cil"lo*scope\, n. [L. oscillare to swing +
   -scope.]
   An electronic measuring instrument which provides a visual
   representation of the time variation of electrical
   quantities, such as voltage or current. It may be used to
   measure the shape of a voltage pulse or the frequency of an
   oscillating voltage. It can also be used to measure
   properties of other physical variables, such as sound or
   light intensity, if they can be translated into electrical
   voltage or current.

   Note: The common cathode-ray oscilloscope uses a cathode-ray
         tube to project a beam of electrons onto the interior
         of a nearly flat surface surface of the tube, which is
         coated with a material which fluoresces when struck by
         the moving electrons. The location of the beam of
         electrons on the target surface is controlled by
         electrodes surrounding the point of origin of the beam,
         which control the horizontal and vertical deflection.
         The degree of deflection from the vertical center can
         be made to represent the electrical variable to be
         measured. The cathode-ray oscilloscope is similar in
         many respects to the most common form of television
         tube. -- os*cil"lo*scop`ic, a.

   Syn: scope, cathode-ray oscilloscope, CRO
        [WordNet 1.5 +PJC]

WordNet (r) 3.0 (2006):

oscilloscope
    n 1: electronic equipment that provides visual images of varying
         electrical quantities [syn: oscilloscope, scope,
         cathode-ray oscilloscope, CRO]

Moby Thesaurus II by Grady Ward, 1.0:

31 Moby Thesaurus words for "oscilloscope":
   Flexowriter typewriter, J-scope, Teleplotter, alphabetical printer,
   digital graph plotter, hard copy, harmonograph, kymograph,
   magnetic recorder, magnetic tape, microcards, microfiche,
   microfilm, oscillograph, oscillograph recorder, oscillometer,
   oscilloscopes, printout, punch cards, punched tape, reader,
   readout, recorder, relay register, seismograph, seismometer,
   seismoscope, tape reader, teletypewriter, vibrograph, vibroscope