a. 1 (context geometry of at least two things, usually lines English) Within the same plane. 2 (context astronomy of multiple planets or other orbiting bodies English) orbiting a central celestial object within the same orbital plane.
The Collaborative International Dictionary
Coplanar \Co*plan"ar\ (k[-o]*pl[=a]n"[~e]r), a. [Pref. co- + plane.] (Math.) Situated in one plane.
adj. lying in the same plane
Douglas Harper's Etymology Dictionary
Usage examples of "coplanar".
And of course the other side of the Moonpoint Wormhole is coplanar with whatever it’s linking up with.
No doubt the only reason Tellman left the problem coplanar was that he didn't have a holo display for his Celest.
If we make a direct coplanar radial approach to Tralus and Talus from the system's exterior, we more or less have to pass by Selonia.