goaf

1. (mining) That part of a mine from which the mineral has been partially or wholly removed.countableuncountable

2. (mining) The waste left in old mine workings; goafing.Examples: "1869, George Fowler, On a Method of Abstracting Explosive Gas from the Goaves of Coal Mines, in Transactions, Volume 18, North of England Institute of Mining Engineers, page 160, In an operation of this kind, primarily for the purpose of extracting the gas out of the goaves, but also with a view to drain the solid coal, it is clear that it is desirable, as much as possible, to draw as directly as possible from the goaf."; "1874, William Hopton, The Prevention of Catastrophes in Mines, in The Hermon Prize Essays: Essays on the Prevention of Explosions and Accidents in Coal Mines, W. M. Hutchings, page 57, Hundreds of lives have been sacrificed by sudden outbursts of gas from the floor and goaf, and miners are constantly working in jeopardy, when a small expense would remove the gas, and prevent the casualties."; "2010, Hua Guo, et al., CSIRO Coal Mining Research and Technologies, Jürgen F. Brune (editor), Extracting the Science: A Century of Mining Research, Society for Mining, Metallurgy and Exploration, page 73, High gas emissions from the longwall goaf is one of the main problems at a number of highly gassy coal mines in Australia, resulting in a significant number of face stoppages. To address the issue of goaf gas control, CSIRO's research aimed at developing optimum goaf gas control."Synonyms: goave, goafing, gob, gobbincountableuncountable