D defs.my
Entry 1 sense Webster, 1913

Goaf

· IPA /ɡəʊf/
01 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 .
pl. Goafs, Goaves ((#))
  1. 1.
    That part of a mine from which the mineral has been partially or wholly removed; the waste left in old workings; -- called also gob .(Mining) Also: gob
Phrases & compounds
To work the goaf — to remove the pillars of mineral matter previously left to support the roof, and replace them with props.