A measure used to describe the width of vision of a dish. Beamwidth is measured as degrees between the 3 dB half power points

A satellite receive dish is characterized by a half-power beamwidth. The signal is received with most power directly along the dish boresight. At increasing greater angles from the boresight, detected signal power drops. The half-power beamwidth is the angular separation between these -3 dB points on the main lobe. Larger antennas have more narrow beamwidths; likewise dishes that receive higher frequency signals have more narrow beamwidths.