- an agate, used as a gem, having polygonal banding such that it suggests the plan of a bastion.
Origin of fortification agate
First recorded in 1880–85
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018
Examples from the Web for fortification agate
Historical Examples of fortification agate
Sometimes they are arranged in angles, presenting the fortification-agate.