What is a Batholith volcano?

A batholith is a very large mass of intrusive igneous rock that forms and cools deep in the Earth's crust. An igneous rock is a type of rock formed through the cooling of lava or magma.

A batholith (from Greek bathos, depth + lithos, rock) is a large mass of intrusive igneous rock (also called plutonic rock), larger than 100 square kilometres (40 sq mi) in area, that forms from cooled magma deep in the Earth's crust.

You can just google it ya know:P