twelve-color problem

twelve-color problem

[′twelv ¦kəl·ər ‚präb·ləm]
(mathematics)
The problem of showing that 12 colors are sufficient to color a map on which each country has at most one colony, and that there is such a map which requires 12 colors.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.