What does periscope mean?
A periscope is an optical viewing instrument that uses mirrors or prisms to let an observer see around a barrier or over an obstacle. Its best-known application is in submarines, where a periscope can remain just below the water's surface while allowing officers to inspect the sea and sky. The word also describes the principle of an elevated or indirect viewpoint, as in a mechanical periscope on a crane or an observation tower. In its rarer verb use, periscope means to look or examine something through such an instrument. The word comes from Greek elements meaning “around” and “look,” accurately reflecting the instrument's function. Although modern periscopes can use sophisticated optics and electronic sensors, the basic idea has long remained recognizable: arranging reflective surfaces so that a line of sight can bend around what would otherwise block it.
An optical instrument using mirrors or prisms to enable a viewer to see around an obstacle or over a concealed position, especially in a submarine.
"The officer looked through the periscope before ordering the submarine to dive."
The word is commonly associated with naval vessels but also applies to cranes, observation towers, and other viewing devices.
To look at or examine something through a periscope.
"The navigator periscoped the inlet from beneath the surface."
This verb is uncommon; “looked through a periscope” is normally preferred.
The standard plural is used for individual periscope instruments.
"The deck contained several periscopes arranged along the submarine's upper hull."
A periscope turns a hidden world into a visible one: the word itself means “looking around.”
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of periscope
The word was formed in the early 19th century from Greek periskopein, meaning “to look around,” which combines the prefix peri- (“around”) with skopein (“to look”). The latter element is also the source of English words such as telescope, microscope, and stethoscope. The compound reflects the characteristic action of the instrument: allowing a person to direct the line of sight around an obstruction.
Related word forms
How periscope is actually used
As a noun, periscope is strongly associated with submarines but is also used for cranes, observation towers, and other devices that provide a view around an obstruction. The verb is uncommon and is more often replaced by the phrase “look through a periscope.”
Easily confused with periscope
A periscope uses mirrors or prisms to view around an obstacle, whereas a telescope uses lenses or mirrors to magnify distant objects.
A periscope is used for viewing over or around obstacles, while a stethoscope is used to listen to internal bodily sounds.