The highest point.
The point, in any trajectory of an object in space, where it is farthest from the Earth.
The point, in an orbit about the Earth, that is farthest from the Earth: the apoapsis of an Earth orbiter.
The point, in an orbit about any planet, that is farthest from the planet: the apoapsis of any satellite.
The highest limit.
A scoring shot for 6 runs.
The greatest value of a set or other mathematical structure, especially the global maximum or a local maximum of a function.
A 147 break; the highest possible break.
A score of 180 with three darts.
An upper bound of a set which is also an element of that set.
The largest value of a batch or sample or the upper bound of a probability distribution.
To the highest degree.