What does the word lack mean?

Usage examples for lack

  1. I think the lack in your life is that you have known so few women; men and women can never understand each other, of course; but they have got to live together and work together; and one ought to live with people whom one does not understand. – Watersprings by Arthur Christopher Benson
  2. There is one at the back, but I have never yet opened that, for lack of a key. – A Set of Rogues by Frank Barrett