Generally, a frequency band left vacant between two bands to protect users in those bands from mutual interference. Guard bands also may be licensed to services whose operating characteristics are dissimilar from those on either side.
This is a narrow piece of bandwidth that acts as a buffer between channel frequency bandwidths, with the intent of reducing interference. (See Guard Channel.)
The gap between tracks (if any) on a magnetic or other recording media. The gap between adjacent frequency channels in a multichannel system Difference between reference black level and blanking level in the luminance signal.