From Longman Dictionary of Contemporary Englishspyglassspy‧glass /ˈspaɪɡlɑːs $ -ɡlæs/ noun [countable] TSEEa small telescope used by sailors in the past
Examples from the Corpus
spyglass• Optics have fascinated Dall since he bought a spyglass telescope from a market stall in his mid-teens.• I passed the spyglass to him. 