from Wiktionary, Creative Commons Attribution/Share-Alike License
- n. That part of a mine from which the mineral has been partially or wholly removed; the waste left in old workings.
from the GNU version of the Collaborative International Dictionary of English
- n. That part of a mine from which the mineral has been partially or wholly removed; the waste left in old workings; -- called also gob .
from The Century Dictionary and Cyclopedia
- n. A stack or cock, as of grain.
- n. A rick of corn in the straw laid up in a barn.
- n. 3. In coal-mining, a space from which coal has been worked away, and which is more or less filled up with refuse.
Compare gob. (Wiktionary)
But experts said that the preferred theory was that a collapse of the mine's roof in the "goaf" - the void left behind after coal is removed - released methane into the mine.