As a Noun: 1. A long, tube-shaped instrument with lenses inside it which you look through in order to make distant things appear larger and nearer. English = telescope. 2. The scientific study of the stars, planets, and other natural objects in space. English = astronomy. 3. A scientist who studies the stars, planets, and other natural objects in space. English = astronomer. As a Verb or Adjective: 1. To use or look through a telescope, to practise the science of astronomy.