noun

• (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.
  "They were able to find the enemy fleet using radar."
• (countable) A type of system using such a method, differentiated by platform, configuration, frequency, power, and other technical attributes.
  "The Ministry of Defence funded the development of an entirely new radar and improved avionics."
• (countable) An installation or instance of such a system or of the transmitting and receiving apparatus.
  "Each of these aircraft has been upgraded with a new radar and a more powerful engine."
• (countable, figuratively) A superior ability to detect something.
  "His sensitive radar for hidden alliances keeps him out of trouble."

verb

• (transitive) To scan with radar, or as if with radar.
  "He radars you while he's sitting in his patrol vehicle under a bridge."

noun

• (dated) Alternative letter-case form of radar.
  "Police traffic RADARs can provide a speed reading on a detected target, but they cannot measure the range to the target."