From Online Dictionary of Crystallography
Macle par reflexion (Fr). Ebenenzwilling, Reflektionszwilling (Ge). Geminato per riflessione (It). Macla de reflexión (Sp).
1. Rational twin mirror plane normal to an irrational line. This lattice plane is common to both twin partners.
2. Irrational twin mirror plane normal to a rational lattice row. This lattice row [uvw] is common to both twin partners.