Spy glass, also known as a spyglass, is a portable telescope used for observing distant objects or surroundings. It is commonly used in the field of navigation, astronomy, and espionage. There are numerous synonyms for the term spyglass, such as a telescope, monocular, binoculars, magnifying glass, optical instrument, and more. Telescope is a synonym for spyglass that is commonly used in astronomy. Monocular is a type of spyglass with a single eyepiece. Binoculars contain two eyepieces and are commonly used for bird watching or hunting. A magnifying glass is a small handheld device used to magnify objects up close. An optical instrument refers to any device that assists in the observation of objects. These synonyms provide a range of options to choose from, depending on the specific use and context required.