convex hull

from The Free On-line Dictionary of Computing (8 July 2008)

convex hull

   <mathematics, graphics> For a {set} S in space, the smallest
   {convex set} containing S.  In the plane, the convex hull can
   be visualized as the shape assumed by a rubber band that has
   been stretched around the set S and released to conform as
   closely as possible to S.

   (1997-08-03)