\Cleav"age\, n.
1. The act of cleaving or splitting.
2. (Crystallog.) The quality possessed by many crystallized
   substances of splitting readily in one or more definite
   directions, in which the cohesive attraction is a minimum,
   affording more or less smooth surfaces; the direction of
   the dividing plane; a fragment obtained by cleaving, as of
   a diamond. See {Parting}.
3. (Geol.) Division into lamin[ae], like slate, with the
   lamination not necessarily parallel to the plane of
   deposition; -- usually produced by pressure.
{Basal cleavage}, cleavage parallel to the base of a crystal,
   or to the plane of the lateral axes.
{Cell cleavage} (Biol.), multiplication of cells by fission.
   See {Segmentation}.
{Cubic cleavage}, cleavage parallel to the faces of a cube.
{Diagonal cleavage}, cleavage parallel to ta diagonal plane.
{Egg clavage}. (Biol.) See {Segmentation}.
{Lateral cleavage}, cleavage parallel to the lateral planes.
{Octahedral, Dodecahedral, or Rhombohedral, {cleavage},
   cleavage parallel to the faces of an octahedron,
   dodecahedron, or rhombohedron.
{Prismatic cleavage}, cleavage parallel to a vertical prism.