A polyalloy was a material used in structures which need to withstand extreme stress. Data's upper spinal support was made from a polyalloy. (TNG: "The Chase")
In 2372, an alien probe composed primarily of duritanium polyalloy was destroyed by the Cardassian ATR-4107. (VOY: "Dreadnought")
The Nausicaan disruptor pistol used polyalloy casing to render the weapon all but invisible to security screeners. (DIS: "Will You Take My Hand?")