Merriam-Webster's Collegiate Dictionary
peri·scope
\\ˈper-ə-ˌskōp\\ noun ETYMOLOGY International Scientific Vocabulary
DATE 1879
: a tubular optical instrument containing lenses and mirrors by which an observer obtains an otherwise obstructed field of view
periscope
1899, formed in Eng. from peri- "around" + -scope "instrument for viewing." Earlier (1865) a technical term in photography.
Oxford Advanced Learner's Dictionary-牛津双解-OALD7
periscopeperi·scope /
5periskEup;
NAmE -skoup /
noun a device like a long tube, containing mirrors which enable the user to see over the top of sth, used especially in a
submarine
(= a ship that can operate underwater) to see above the surface of the sea
潜望镜 Webster's Third New International Dictionary, Unabridged
peri·scope
\ˈperəˌskōp\ noun
Etymology: International Scientific Vocabulary peri- + -scope
: an optical instrument by which an observer (as on a submerged submarine or in work with highly radioactive materials) looks through or as if through an eyepiece into a mirror or totally reflecting prism attached at an angle of 45 degrees to one end of a tube containing a system of lenses and obtains an otherwise obstructed field of view from another mirror or prism correspondingly attached to the other end of the tube