Universal, no, but physicists agree, and, really, who else matters? X-rays are emitted by electrons (atomic transitions or bremsstrahlung); gamma rays by nuclear transitions. Those definitions have been pretty well agreed upon by physicists for at least the last 15 years.
Astronomers, however, seem to characterize photons only by energy, which kind of makes sense if you realize that they frequently don't know the origin of the observed photons and build instruments for energy ranges instead.
But nonetheless it is still incorrect to characterize these photons as "x-rays."