Trachyandesite is one of the important type of rocks. If we have to define Trachyandesite in general, Trachyandesite is an extrusive igneous rock.. Trachyandesite comes under Igneous Rocks. All Igneous Rocks have similar properties and formation process. Along with Trachyandesite Definition, know more about the History of Trachyandesite, Etymology of Trachyandesite in next sections.