Sink  —v. (past sank or sunk; past part. Sunk or as adj. Sunken) 1 fall or come slowly downwards. 2 disappear below the horizon. 3 a go or penetrate below the surface esp. Of a liquid. B (of a ship) go to the bottom of the sea etc. 4 settle comfortably. 5 a decline in strength etc. B (of the voice) descend in pitch or volume. 6 cause or allow to sink or penetrate. 7 cause (a plan, person, etc.) To fail. 8 dig (a well) or bore (a shaft).