What does the word perpendicular mean?

Usage examples for perpendicular

  1. It was trying to the nerves, for while on one side rose a perpendicular wall of rock, on the other the precipice went sheer down for several hundred feet, with a roaring torrent at the bottom. – On the Banks of the Amazon by W.H.G. Kingston
  2. Looking back at the solid and apparently perpendicular rock, nearly a mile high, it seemed impossible that any one could ascend to the top. – The Lure of the Camera by Charles S. Olcott