The Collaborative International Dictionary of English v.0.48:

Sink \Sink\ (s[i^][ng]k), n.
   1. A drain to carry off filthy water; a jakes.
      [1913 Webster]

   2. A shallow box or vessel of wood, stone, iron, or other
      material, connected with a drain, and used for receiving
      filthy water, etc., as in a kitchen.
      [1913 Webster]

   3. A hole or low place in land or rock, where waters sink and
      are lost; -- called also sink hole. [U. S.]
      [1913 Webster]

   4. The lowest part of a natural hollow or closed basin whence
      the water of one or more streams escapes by evaporation;
      as, the sink of the Humboldt River. [Western U. S.]
      [Webster 1913 Suppl.]

   Sink hole.
      (a) The opening to a sink drain.
      (b) A cesspool.
      (c) Same as Sink, n., 3.
          [1913 Webster]