a combining form with the meaning “pertaining to stars or celestial bodies, or to activities, as spaceflight, taking place outside the earth's atmosphere,” used in the formation of compound words: astronautics; astrophotography.
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019
British Dictionary definitions for astro-
indicating a heavenly body, star, or star-shaped structureastrology; astrocyte
indicating outer spaceastronautics
Word Origin for astro-
from Greek, from astron star
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
Science definitions for astro-
A prefix that means star (as in astrophysics), celestial body (as in astronomy), or outer space (as in astronaut).
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.