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.
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.
3. A hole or low place in land or rock, where waters sink and
are lost; -- called also sink hole. [U. S.]
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.]
(a) The opening to a sink drain.
(b) A cesspool.
(c) Same as Sink, n., 3.