Crystallography. noting or pertaining to a system of crystallization in which three equal axes intersect at angles of 60° on one plane, and the fourth axis, of a different length, intersects them perpendicularly.
British Dictionary definitions for pseudohexagonal
having six sides and six angles
of or relating to a hexagon
(crystallog) relating or belonging to the crystal system characterized by three equal coplanar axes inclined at 60° to each other and a fourth longer or shorter axis at right angles to their plane See also trigonal
Relating to a crystal having three axes of equal length intersecting at angles of 60° in one plane, and a fourth axis of a different length that is perpendicular to this plane. The mineral calcite has hexagonal crystals. See illustration at crystal.