Pronunciation: (per'u-skōp"), [key]
1. an optical instrument for viewing objects that are above the level of direct sight or in an otherwise obstructed field of vision, consisting essentially of a tube with an arrangement of prisms or mirrors and, usually, lenses: used esp. in submarines.
2. a periscopic lens.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.