of three metals.
Engraving. (of an offset plate) consisting of a face layer of chromium, stainless steel, or chemically prepared aluminum over a layer of copper with a strengthening backup layer of steel or other metal.

Origin of trimetallic

First recorded in 1885–90; tri- + metallic Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019