What does the word sink mean?

Usage examples for sink

  1. But it was what they could rise to, not what they could sink to, that made them great. – Misalliance by George Bernard Shaw
  2. Can you sink anything with her?" – The World Peril of 1910 by George Griffith
  3. And always it had been to learn that she had been mistaken; always it had been to feel the heart sink just a little lower than before. – The Cow Puncher by Robert J. C. Stead