What does "cartesian" mean?

Cartesian: Of or pertaining to the French philosopher René Descartes, or his philosophy. The Cartesion argument for reality of matter. Sir W. Hamilton. Cartesian coördinates (Geom), distance of a point from lines or planes; -- used in a system of representing geometric quantities, invented by Descartes. -- Cartesian devil, a small hollow glass figure, used in connection with a jar of water having an elastic top, to illustrate the effect of the compression or expansion of air in changing the specific gravity of bodies. -- Cartesion oval (Geom.), a curve such that, for any point of the curve mr + m'r' = c, where r and r' are the distances of the point from the two foci and m, m' and c are constant; -- used by Descartes.