guard band

Short definition from Wiktionary

Noun

1. 1
   An unused part of the radio spectrum between bands, for the purpose of preventing interference.
2. 2
   The unrecorded space between tracks on magnetic tape or other media which prevents the signals on adjacent tracks from interfering with each other.
3. 3
   The amount by which minimum product specifications are increased to ensure that, even with measurement uncertainty, the product will meet the minimum specifications with a specified level of confidence.
4. 4
   A virtual area of the screen, bordering the real screen, to which any rendering is ignored, used to simplify clipping.