1. The deflection or the displacement of an electron beam from its straight-line path of an electron beam by means of an electrostatic field which is produced by electrodes on opposite sides of a beam. 2. A technique for modifying the path of a stream of charged particles by the use of an electric field applied across from side to side or at right angles to the path of the particles.
3. The movement of an electron beam as a result of the electrostatic field produced by electrodes on either side of the beam.

It is primarily used in cathode-ray tubes for oscilloscopes and in old-fashioned television picture tubes.

The electron beam is bent toward a positive electrode and bent away from a negative electrode or it is attracted to a positive electrode and repelled by the negative electrostatic charges.