altiscope

from The Century Dictionary.

• noun An instrument consisting of an arrangement of lenses and mirrors in a telescopic tube, extensible vertically, by means of which it is possible to look over objects intervening between the observer and the object to be seen.

from the GNU version of the Collaborative International Dictionary of English.

• noun An arrangement of lenses and mirrors which enables a person to see an object in spite of intervening objects. Since the early 1900's, most commonly called periscope.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun An arrangement of lenses and mirrors making it possible to see around obstructing objects.