Doppler is a noun used chiefly in physics and medicine to describe effects or phenomena caused by the motion of a source relative to an observer (e.g., the Doppler effect). It also appears in medical imaging, where it refers to a type of ultrasound technique that measures blood flow. The term honors Christian Andreas Doppler, whose discovery named the phenomenon. In usage, it denotes a principle, device, or measurement related to motion-based frequency shifts.
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