/i lips"/ , n. Geom.
a plane curve such that the sums of the distances of each point in its periphery from two fixed points, the foci, are equal. It is a conic section formed by the intersection of a right circular cone by a plane that cuts the axis and the surface of the cone. Typical equation: ( x 2 / a 2 ) + ( y 2 / b 2 ) = 1. If a = b the ellipse is a circle. See diag. under conic section .
[ 1745-55; ellipsis ELLIPSIS; or by back formation from the pl. ELLIPSES ]