enormously large in amount or quantity, to the point of being unreasonable or difficult to understand;
e.g. He was presented with an astronomical bill after his stay at the hospital.
(adjective)
relating to the study of space beyond the earth's atmosphere, celestial bodies and their properties, and the physical universe, i.e. relating to astronomy;
e.g. She uses a telescope and many complex instruments to collect astronomical data for her experiments.