/haf"playn', hahf"-/, n. Math.
the part of the plane on one side of a straight line of infinite length in the plane.
[1890-95]
* * *
half-plane «HAF PLAYN, HAHF-», noun.
Geometry. the part of a plane on one side of a straight line drawn in the plane. The line itself is usually not considered part of the half-plane.
Useful english dictionary. 2012.