Are you referring to the hybrid cross between Juniperus chinensis and J. sabina...which is called J. x media or J. x pfitzeriana?

No. In botanical terms, 'media' means average or middle, so a hybrid that had 'x media' as the species portion of the binomial means that plant is intermediate in appearance, habit or morphology between the two parent species that resulted in the hybrid. The species or second portion of a botanical binomial is never a "placeholder" - it always has a meaning or significance.