\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.
                                               Hamilton.
{Cartesian co["o]rdinates} (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.

\Car*te"sian\, n.
An adherent of Descartes.