from The American Heritage® Dictionary of the English Language, 4th Edition
- n. Any of various dark gray sandstones that contain shale.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. Alternative form of greywacke.
from the GNU version of the Collaborative International Dictionary of English
- n. A conglomerate or grit rock, consisting of rounded pebbles and sand firmly united together.
from The Century Dictionary and Cyclopedia
- n. In geology, a compact aggregate of rounded or subangular grains of various silicious rocks, held together by a paste which is usually silicious.
Partial translation of German Grauwacke : grau, gray + Wacke, rock (from Middle High German, from Old High German waggo, boulder; see wegh- in Indo-European roots).(American Heritage® Dictionary of the English Language, Fourth Edition)