Definitions for "BLUE SHIFT"
A reduction of light wavelengths, caused by a motion toward the observer. So called because blue light has shorter wavelengths than red light.
Apparent shortening of the wavelength due to Doppler effect, of radiation received from a source in motion toward the observer.
a shift in electromagnetic radiation towards the blue (or shorter end of the spectrum) which is the result of movement towards the observer
The phenomenon in which a source of light moving toward you appears to have a higher frequency.