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an optical instrument that provides a view of an otherwise obstructed field

an optical instrument that provides a view of an otherwise obstructed field

an optical instrument of tubular shape containing an arrangement of lenses and mirrors (or prisms), allowing a person to observe a field of view otherwise obstructed, as beyond an obstructing object or (as in submarines) above the surface of the water.

an optical instrument of tubular shape containing an arrangement of lenses and mirrors (or prisms), allowing a person to observe a field of view otherwise obstructed, as beyond an obstructing object or (as in submarines) above the surface of the water.

An instrument consisting of a revolving prism capable of reflecting light from any quarter down an upright tube: used as an outlook ever the water for guiding submarine boats when submerged.

n. [Greek] A general view.