zero-sum definition by Webster's New World
Webster's New World College Dictionary Copyright © 2010 by Wiley Publishing, Inc., Cleveland, Ohio. Used by arrangement with John Wiley & Sons, Inc.
in game theory, designating or of a situation, competition, etc. in which a gain for one must result in an equal loss for another or others
zero-sum definition by American Heritage Dictionary
Of or relating to a situation in which a gain is offset by an equal loss: “. . .under the zero-sum budgeting system that governs federal spending, the money for spinal research is likely to be deducted from some other research account” (Daniel S. Greenburg).