absolute magnitude

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun The intrinsic brightness of a celestial body, measured in magnitudes, computed as if viewed from a distance of 10 parsecs, or 32.6 light years.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun astronomy The intrinsic luminosity that a celestial body would have if viewed from a distance of 10 parsecs or 32.6 light years.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun (astronomy) the magnitude that a star would have if it were viewed from a distance of 10 parsecs (32.62 light years) from the earth