Definition of "schistosity"

It will become apparent from the following discussion that some of the various structures which are grouped together as cleavage may correspond to a schistosity and/or foliation. Accordingly, Wilson defines rock cleavage (and schistosity) as a planar structure, usually distinct from stratification, which permits rocks to be fractured or cleaved into thin slices.

1990, N[eville] J. Price, J[ohn] W. Cosgrove, “Rock Cleavage and Other Tectonic Fabrics”, in Analysis of Geological Structures, Cambridge: Cambridge University Press, page 434