hemisymmetric

from The Century Dictionary.

• Symmetrical with regard to one axis only, as the parabola in contradistinction to the ellipse and hyperbola.
• Pertaining to or exhibiting hemisymmetry. See hemisymmetry, 2.
• In crystallography, hemihedral; characterized by hemisymmetry, that is, by a grade of symmetry which requires only half the faces that belong to the corresponding form of the holosymmetric (holohedral) type. See symmetry.