In general, pertaining to material, as a particle, moving at speeds which are an appreciable fraction of the speed of light thus increasing the mass
relating or subject to the special or the general theory of relativity; "relativistic quantum mechanics"; "relativistic increase in mass"; "radiation from relativistic particles"
(physics) the mass of a body in motion relative to the observer: it is equal to the rest mass multiplied by a factor that is greater than 1 and that increases as the magnitude of the velocity increases