Radar (an acronym for RAdio Detection And Ranging) is
[a]n instrument that emits a narrow beam of electromagnetic pulses (radio waves) in a specific direction and measures the time, intensity, or other characteristics of the energy that returns from targets or objects. Radar imagery can be obtained at night or through clouds and smoke. Radar images provide a unique visual impression, and advanced analysis of radar imagery usually requires specific experience, knowledge, and facilities.
a method of detecting objects and determining their position, velocity, or other characteristics by analysis of high frequency radio waves reflected from their surfaces.