relativistic

from WordNet (r) 3.0 (2006)

relativistic
    adj 1: relating or subject to the special or the general theory
           of relativity; "relativistic quantum mechanics";
           "relativistic increase in mass"; "radiation from
           relativistic particles"
    2: of or relating to the philosophical doctrine of relativism

from The Collaborative International Dictionary of English v.0.48

Relativistic \Rel`a*tiv*ist"ic\, a.
   1. of, pertaining to, or in conformity with the {theory of
      relativity}; as, the relativistic increase of mass with
      velocity.
      [PJC]

   2. moving at a speed sufficiently high that the changes of
      mass or time dilation predicted by the theory of
      relativity may be observed; moving at a significant
      fraction of the speed of light; as, relativistic
      electrons.br/ [PJC]