game theory

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

• noun A mathematical method of decision-making in which a competitive situation is analyzed to determine the optimal course of action for an interested party, often used in political, economic, and military planning.

from the GNU version of the Collaborative International Dictionary of English.

• noun A branch of mathematics that deals with strategies for maximizing gains or minimizing losses in competitive situations having defined constraints and involving random factors.

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

• noun mathematics, economics A branch of applied mathematics that studies strategic situations in which individuals or organisations choose various actions in an attempt to maximize their returns.

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

• noun (economics) a theory of competition stated in terms of gains and losses among opposing players