from Wiktionary, Creative Commons Attribution/Share-Alike License
- adj. Having the shape of a bipyramid
from the GNU version of the Collaborative International Dictionary of English
- adj. Consisting of two pyramids placed base to base; having a pyramid at each of the extremities of a prism, as in quartz crystals.
from The Century Dictionary and Cyclopedia
- In crystallography, having the form of two pyramids joined base to base, as quartz crystals.
From bi- + pyramidal (Wiktionary)