What does the word sentinel mean?

Usage examples for sentinel

  1. But had one not need to walk with a guard, and to have a sentinel stand at one's door for this? – The Works of John Bunyan Volume 3 by John Bunyan
  2. There was a simultaneous movement towards the shattered apparatus, about which a small contingent of villagers, who had availed themselves of the withdrawal of the sentinel, had now assembled. – Marriage by H. G. Wells
  3. At the gate I was again condemned to hear from the sentinel, " Where has the gentleman left his shadow?" – Peter Schlemihl by Adelbert von Chamisso