The Collaborative International Dictionary of English v.0.48:
Cartesian \Car*te"sian\, a. [From Renatus Cartesius, Latinized
from of Ren['e] Descartes: cf. F. cart['e]sien.]
Of or pertaining to the French philosopher Ren['e] Descartes,
or his philosophy.
The Cartesion argument for reality of matter. --Sir W.
Cartesian coordinates (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.