Definitions
from Wiktionary, Creative Commons Attribution/ShareAlike License
 n. A change in the wavelength of light, in which the wavelength is shorter than when it was emitted at the source.
Etymologies
Examples

"blueshift", methods for determining whether a star is moving away from or towards you respectively.

The spectrograph allowed the researchers to monitor the redshift or blueshift of light as the planet orbited the star.
Second Exoplanet with Retrograde Orbit Discovered  Universe Today

First with the dipole motion, the redshift/blueshift pattern caused by our motion.

Because acceleration is so dominant, the net effect is that the potential decays while the photon traverses the well, meaning that the photon emerges with a slight net blueshift, compared to how it entered.

So the initial acceleration toward the observer (which causes blueshift) is very high.

This is the gravitational blueshift effect that Prof. Peacock describes in his “diatribe” and which Matt, Geraint, Luke and Berian allude to in their recent radar ranging paper.

That is, the collapse action of the cosmic gravitation imparts a blueshift (like an accelerating moving sidewalk) to the photon, which exactly offsets and compensates for its classical Doppler redshift.

In the meanvelocity Doppler model, the blueshift acceleration experienced by the travelling photon is essentially the same contractive gravitational acceleration experienced by the galaxies in the Hubble Flow, so the photon does not experience any gravitational time dilation which differs from the underlying time dilation inherent in the FLRW metric.

I believe we would, except that the redshift of the classical Doppler Effect is exactly cancelled out by the gravitational blueshift caused by the cosmic gravitation field.

Prof. Peacock combines an integration of SR redshift and gravitational blueshift.
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