noun
Usage: usually capitalized 1st C
1. : either of two coordinates for locating a point on a plane being the distances of the point from each of two infinite intersecting straight-line axes of reference usually designated as X and Y measured in each case parallel to the other axis and each coordinate being given arbitrarily an algebraic sign according to the direction in which it extends from the reference axis to the point
2. : any one of three coordinates for locating a point in space being the distances from each of three intersecting coordinate planes measured in each case parallel to that one of three straight-line axes that is the intersection of the other two planes — compare rectangular coordinate