cleavage

n. 1. The act of cleaving or splitting. [ 1913 Webster ]

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. [ 1913 Webster ]

3. (Geol.) Division into laminæ, like slate, with the lamination not necessarily parallel to the plane of deposition; -- usually produced by pressure. [ 1913 Webster ]

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 cleavage,
Dodecahedral cleavage, or
Rhombohedral cleavage, cleavage parallel to the faces of an octahedron, dodecahedron, or rhombohedron. --
Prismatic cleavage, cleavage parallel to a vertical prism. [ 1913 Webster ]