- The definition of an astronomer is a scientist who studies matter and objects in outer space.
Someone who observes the stars and makes notes about their movements is an example of an astronomer.
astronomer definition by Webster's New World
Webster's New World College Dictionary Copyright © 2010 by Wiley Publishing, Inc., Cleveland, Ohio. Used by arrangement with John Wiley & Sons, Inc.
an expert in astronomy
astronomer definition by American Heritage Dictionary
One who specializes in astronomy.