from The American Heritage® Dictionary of the English Language, 4th Edition
- n. Poorly crystallized diamonds used for industrial cutting and abrasion.
- n. A carbonado.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. Poor quality diamond, used for industrial cutting or abrasion; a poorly crystallized diamond.
from the GNU version of the Collaborative International Dictionary of English
- n. Imperfectly crystallized or coarse diamonds, or fragments made in cutting good diamonds which are reduced to powder and used in lapidary work.
from The Century Dictionary and Cyclopedia
- n. A collective name for diamonds of inferior quality, especially such as have a radiating crystallization, so that they will not take a polish.
- n. An amorphous variety of diamond, brown, gray, or black in color, and known also as black diamond or carbonado, found massive in Brazil in association with pure diamonds.
Probably from Dutch boort.(American Heritage® Dictionary of the English Language, Fourth Edition)