Definitions
1.nounThe point, in an orbit about the Earth, that is furthest from the Earth: the apoapsis of an Earth orbiter.
2.noun(more generally) The point, in an orbit about any planet, that is farthest from the planet: the apoapsis of any satellite.
3.noun(possibly obsolete outside astrology) The point, in any trajectory of an object in space, where it is furthest from the Earth.
4.nounThe highest point.