| 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. |
| astro- or astr- pref.
[Greek, from astron, star; see ster-3 in Indo-European roots.] |
| astro-
A prefix that means "star" (as in astrophysics), "celestial body" (as in astronomy), or "outer space" (as in astronaut). |
r