Triangulation is defined as a method of surveying an area by dividing it into triangles.(noun)
An example of triangulation is determining the total area of an island by setting a fixed point in the middle of the island, dividing the island into triangles from that point, determining that one side of a triangle is 1000 feet long and that the triangle makes a 180 degree angle, and then determining the length of the other side based on this information.
See triangulation in Webster's New World College Dictionary
Origin: ML triangulatio
See triangulation in American Heritage Dictionary 4
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