The term 'kind of radar' can be answered with the word 'Doppler', which is a seven-letter word. Doppler radar is a type of radar that uses the Doppler effect to measure the velocity of objects. It works by measuring the frequency of the reflected signal and comparing it to the frequency of the transmitted signal. This allows it to measure the speed of objects, such as cars or aircraft, in motion. Doppler radar is used in many applications, including weather forecasting, air traffic control, and military operations.