a depression in the ground communicating with a subterranean passage (especially in limestone) and formed by solution or by collapse of a cavern roof(noun.object)
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.(noun)
source: webster1913
verb (v)
fall or descend to a lower place or level(verb.motion)
To fall by, or as by, the force of gravity; to descend lower and lower; to decline gradually; to subside; as, a stone sinks in water; waves rise and sink; the sun sinks in the west.(verb)
source: webster1913
To cause to sink; to put under water; to immerse or submerge in a fluid; as, to sink a ship.(verb)