from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. The face of a crystal parallel to two of the axes.
from the GNU version of the Collaborative International Dictionary of English
- n. A plane parallel to two of the crystalline axes.
from The Century Dictionary and Cyclopedia
- n. In crystallography, a plane parallel to two of the crystallographic axes: as, the basal pinacoid, or base parallel to the lateral axes.
- n. Some authors extend the use of this term to embrace any form which has but two parallel faces; according to this usage, all the possible faces of a holosymmetric triclinic crystal are called pinacoids.
Ancient Greek πινάκιον (pinakion, "slab, tablet") + -oid. (Wiktionary)