- For a device such as a filter, amplifier, waveguide, or transmission line, the frequency at which the attenuation increases rapidly. For example, the frequency above which the output of an electron tube is no longer useful. Also called cutoff (2), cutoff frequency (1), or critical frequency.
- The upper and lower frequencies at which the gain of an amplifier, such as a transistor, drops 3 decibels, or another reference amount. Also called cutoff (3), or cutoff frequency (2).
- For a given transmission mode in a waveguide, the frequency below which a traveling wave can not be maintained. That is, the waveguide functions efficiently only above this frequency. Also called cutoff (4), cutoff frequency (3), or waveguide cutoff.