Hemihedry
From Online Dictionary of Crystallography
Hémiédrie (Fr). Hemiedria (Sp). Emiedria (It). 半面像 (Ja)
Definition
The point group of a crystal is called hemihedry if it is a subgroup of index 2 of the point group of its lattice.
See also
Section 9.1 of International Tables of Crystallography, Volume A