means a technique for detecting exoplanets by measuring the periodic red-and-blue shift in a star's light as an orbiting planet's gravity tugs it slightly back and forth.

from named for christian doppler, who in 1842 explained why pitch shifts as a sound source moves toward or away from you; astronomers later realized the same shift applies to starlight, and that an unseen planet's gravity makes its star flinch on a predictable rhythm.