1) Scientific theory 
A term used to describe any situation in which Einstein's theories of relativity makes predictions that are significantly different from those of classical (Newtonian) physics.
[adj] - of or relating to the philosophical doctrine of relativism 2. [adj] - (physics) relating or subject to the special or the general theory of relativity
adjective relating or subject to the special or the general theory of relativity; `relativistic quantum mechanics`; `relativistic increase in mass`; `radiation from relativistic particles`
Traveling at a significant fraction of the speed of light.