What does the word certain mean?

Usage examples for certain

  1. " We shall never get them to live here, that's certain," said Blair. – White Fire by John Oxenham
  2. I am, or at least others are certain. – Moon of Israel by H. Rider Haggard
  3. Of course there were certain troubles to be got over in connection with your mother's presence to- day. – An Amiable Charlatan by E. Phillips Oppenheim