What does the word knock mean?

Usage examples for knock

  1. To- morrow sometime I shall enter the east wing of this building if I have to knock down all the doors on the place. – A Fool and His Money by George Barr McCutcheon
  2. Maybe this will knock some sense into your head." – Jess of the Rebel Trail by H. A. Cody
  3. There came another knock at the door. – Kent Knowles: Quahaug by Joseph C. Lincoln