Twinning by pseudomerohedry
From Online Dictionary of Crystallography
Maclage par pseudomériédrie (Fr). Macla por pseudomeriedria (Sp). Geminazione per pseudomeroedria (It). 偽欠面双晶 (Ja)
A lattice is said to be pseudosymmetric if at least a lattice row or/and a lattice plane approximately correspond to elements of symmetry; these elements can act as twinning operators (e.g., a monoclinic lattice with its oblique angle close to 90° is pseudo-orthorhombic and thus shows two pseudo twofold axes and two pseudo mirror planes).
Chapter 3.3 of International Tables of Crystallography, Volume D