Glass is a :

Glass is scientifically defined as a non-crystalline or amorphous solid formed through the process of vitrification. Vitrification involves heating materials until they liquefy and then cooling the liquid rapidly so that it passes through a glass transition to a solid state without crystallizing. This results in a material that exhibits the glass transition phenomenon and maintains a disordered atomic structure similar to a supercooled liquid [1]. Unlike crystalline materials, which possess long-range repeating 3D patterns, glass lacks such order. While it appears solid on short timescales, its structural nature as a 'solidified material' derived from a melt leads to its classification as a vitrified or supercooled liquid [1]. It is distinct from polymeric materials (though some polymers can form glasses) and is certainly not a crystalline material or a simple semisolid.

Sources

1. [1] https://en.wikipedia.org/wiki/Vitrification