The Collaborative International Dictionary of English v.0.48:

Brachypinacoid \Brach`y*pin"a*coid\, n. [Gr. brachy`s short + E.
   pinacoid.] (Crytallog.)
   A plane of an orthorhombic crystal which is parallel both to
   the vertical axis and to the shorter lateral (brachydiagonal)
   axis.
   [1913 Webster]