n (uncountable) A method of detecting distant objects and determining their position, velocity, or other characteristics by analysis of sent radio waves (usually microwaves) reflected from their surfaces
n (countable) A type of system using such a method, differentiated by platform, configuration, frequency, power, and other technical attributes.
n (countable) An installation of such a system or of the transmitting and receiving apparatus.
n (countable, figuratively) A superior ability to detect something.
v To scan with radar, or as if with radar.
n Acronym of radio detection and ranging.