Source : Webster's Revised Unabridged Dictionary (1913)

Sludge \Sludge\, n. [CF. {Slush}.]
   1. Mud; mire; soft mud; slush. --Mortimer. Tennyson.

   2. Small floating pieces of ice, or masses of saturated snow.
      --Kane.

   3. (Mining) See {Slime}, 4.

   {Sludge hole}, the hand-hole, or manhole, in a steam boiler,
      by means of which sediment can be removed.