x1 orbits a (common) barycenter with x2, with orbital characteristics/parameterz x3.
Typically but not necessarily, x2 will be the more massive object (compared to x1) unless the barycenter is outside of both bodies; nonetheless, this word is technically symmetric between x1 and x2 if no external force is being applied to the system or either body (causing a deviation from orbit). See also: "mluni". If "mluni" is strictly about objects which orbit planets or artificial objects which orbit stellar or smaller objects (if they orbit them at all), then this word is a generalization; it can reference such objects, or planets around their sun(s), or satellite galaxies, among others. If "mluni" has a definition which encompasses this one in terms of scope, then this one should probably be deleted.