Sump /(?)/

Sump

n.
  1. A round pit of stone, lined with clay, for receiving the metal on its first fusion. (Metal.)
  2. The cistern or reservoir made at the lowest point of a mine, from which is pumped the water which accumulates there.
  3. A pond of water for salt works.
  4. A puddle or dirty pool. [Prov. Eng.]

Phrases & Compounds
Sump fuse
a fuse used in blasting under water.
Sump men
the men who sink the sump in a mine.