I have heard the term 'Doppler spread' in reference to meteorological (weather) RADAR detecting hydrometeors (rain) where the 'return' signal is not just one 'pure' tone but rather a range of tones with what might be termed 'Doppler spread' or as they express it as "Spectrum Width". This is due to targets (rain and hail) moving at varying speeds, reflecting RADAR energy with varying amounts of simple Doppler shift.