periscope
n.
viewing apparatus on a submarine, 1899, formed in English from peri- "around" + -scope "instrument for viewing." Earlier (1865) a technical term in photography. Related: Periscopic.
〔李〕[peri-=around 周围；scope=an instrument for observing 观察仪器 →] n. an instrument for seeing things around at a higher level 潜望镜