The Collaborative International Dictionary of English v.0.48:

Sump \Sump\, n. [Cf. G. sumpf a sump in a mine, a swamp, akin to
   LG. sump, D. somp a swamp, Dan. & Sw. sump, and perhaps to E.
   swamp.]
   1. (Metal.) A round pit of stone, lined with clay, for
      receiving the metal on its first fusion. --Ray.
      [1913 Webster]

   2. The cistern or reservoir made at the lowest point of a
      mine, from which is pumped the water which accumulates
      there.
      [1913 Webster]

   3. A pond of water for salt works. --Knight.
      [1913 Webster]

   4. A puddle or dirty pool. [Prov. Eng.]
      [1913 Webster]

   Sump fuse, a fuse used in blasting under water.

   Sump men (Mining), the men who sink the sump in a mine.
      [1913 Webster]

WordNet (r) 3.0 (2006):

sump
    n 1: an oil reservoir in an internal combustion engine
    2: a well or other hole in which water has collected
    3: a covered cistern; waste water and sewage flow into it [syn:
       cesspool, cesspit, sink, sump]