1. A thermodynamic quantity that is the difference between the internal energy of a system and the product of its absolute temperature and entropy.
2. A thermodynamic quantity that is the difference between the enthalpy and the product of the absolute temperature and entropy of a system. Also called Gibbs free energy.

The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2009. Published by Houghton Mifflin Company. All rights reserved.