cosmological constant

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

• noun A constant introduced into the general theory of relativity, proportional to the energy density of the vacuum, and related to the rate of expansion or contraction of the universe. The vacuum energy represented by the cosmological constant is a form of dark energy.

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

• noun physics A term added by Albert Einstein to his equations of general relativity in order to account for a supposed static universe.

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

• noun an arbitrary constant in the equations of general relativity theory