sink

noun

1.
plumbing fixture consisting of a water basin fixed to a wall or floor and having a drainpipe
2.
(technology) a process that acts to absorb or remove energy or a substance from a system
Antonym:
source
3.
a depression in the ground communicating with a subterranean passage (especially in limestone) and formed by solution or by collapse of a cavern roof
4.
a covered cistern; waste water and sewage flow into it