absissa - n.
(pl. abscissae or abscissas) Math.
1 (in a system of coordinates) the shortest distance from a point to the vertical or y-axis, measured parallel to the horizontal or x-axis; the Cartesian x-coordinate of a point (cf. ORDINATE).
2 the part of a line between a fixed point on it and an ordinate drawn to it from any other point. [mod.L abscissa (linea) fem. past part. of abscindere absciss- (as AB-, scindere cut)]