1. An oscillation of the electric or magnetic field associated with the propagation of electromagnetic radiation.
2. A wave which consists of both electric and magnetic variation.
3. A wave of electromagnetic radiation generated by the oscillation of a charged particle and characterized by periodic variations of electric and magnetic fields.
4. A wave of energy made up of an electric and a magnetic field which is generated when an electric charge oscillates or is accelerated.

Light waves and radio waves are electromagnetic waves, according to their frequencies and wavelengths.

The primary kinds of electromagnetic waves, ranging from the longest to the shortest wave length, are long radio waves, short radio waves, infrared rays, visible light, ultraviolet light, X-rays, and gamma rays.

1. A device that allows electromagnetic waves of certain frequencies to pass while effectively attenuating (weakening) others.
2. Any device to transmit electromagnetic waves of desired frequencies while substantially reducing the strength of all of the other frequencies.