Hubble's constant

from The American Heritage® Dictionary of the English Language, 4th Edition

• n. A ratio expressing the rate of apparent expansion of the universe, equal to the velocity at which a typical galaxy is receding from Earth divided by its distance from Earth.

from Wiktionary, Creative Commons Attribution/Share-Alike License

• n. Alternative spelling of Hubble constant.

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

• n. (cosmology) the ratio of the speed of recession of a galaxy (due to the expansion of the universe) to its distance from the observer; the Hubble constant is not actually a constant, but is regarded as measuring the expansion rate today