What does the word sworn mean?

Usage examples for sworn

  1. I can promise you that as well as if he had sworn it." – In the Carquinez Woods by Bret Harte
  2. I'd have sworn it was nearly daylight. – The Abandoned Room by Wadsworth Camp
  3. Since his marriage he had sworn off the school, as he couldn't spare the money with a wife to keep. – Jonah by Louis Stone