spacelike
Adjective
Meaning
having the properties of space
(physics, of the interval between two events in spacetime) lying outside each other's light cone, so that no information can pass from one to the other
(mathematics, of a four-vector) having a space component of greater magnitude than its time component multiplied by the speed of light
Source: en.wiktionary.orgExamples
Moreover, since tachyons are constrained to the spacelike portion of the energy–momentum graph, it could not slow down to subluminal speeds.
In special relativity, this notion is extended by adding the appropriate timelike quantity to a spacelike vector quantity, and we have 4d vectors, or " four vectors ", in Minkowski spacetime.
This is true more generally: certain pairs of "timelike" and "spacelike" quantities naturally combine on equal footing under the same Lorentz transformation.
For two spacelike separated events x 1 and x 2 there are inertial systems in which x 1 is first and others in which x 2 is first.
This turns out to imply that the 5th coordinate is spacelike in its signature in the metric.