Glass is a solid. There are certain characteristics of the 3 stages of matter (solid, liquid, gas). A solid has a fixed volume and shape. The particles of a solid vibrate. They do not move past one another as they do in a liquid or a gas.
Refer to the link below for more information on solids, liquids, and gases. It breaks down the characteristics of each and includes visual examples of how the particles move in each.
Glass is a solid. It has definite shape and definite volume. In addition, the particles of a solid are close together and movement is minimal. (According to kinetic theory, all matter is made of of particles that are moving.) This particular arrangment of particles defines matter in the solid state.
glass is a solid as it is of a fixed shape and size.