Periscope (noun)

1. A device, typically used on submarines and tanks, that allows the viewer to see things at a higher level or outside of the direct line of sight.
2. An optical instrument consisting of mirrors or prisms for viewing an object that is not in the direct line of sight.

Origin:

From greek peri- "around" + skopos "watcher".

Examples:

1. The submarine used a periscope to look above the water surface.
2. The tank had a periscope to look over the terrain.
3. The periscope allowed the viewer to see over the wall.
4. The spy used a periscope to look into the enemy's base.
5. The periscope was a vital tool for the submarine crew.