What is "sullage piece"

Sullage \Sul"lage\, n. [Cf. Suillage, Sulliage.]

1. Drainage of filth; filth collected from the street or highway; sewage. [Obs.]

   The streets were exceedingly large, well paved, having many vaults and conveyances under them for sullage.
   --Evelyn.

2. That which sullies or defiles. [Obs.]

   It is the privilege of the celestial luminaries to receive no tincture, sullage, or difilement from the most noisome sinks and dunghills here below.
   --South.

3. (Founding) The scoria on the surface of molten metal in the ladle.

4. (Hydraul. Engin.) Silt; mud deposited by water.

   Sullage piece (Founding), the sprue of a casting. See Sprue, n., 1 (b) .