Glass is a Liquid or Solid

Glass is hard, it must be a supercooled liquid. Glass, however, is actually neither a liquid—supercooled or otherwise—nor a solid. It is an amorphous solid—a state where those two states(liquid and Solid) of matter, In a liquid, the molecules move freely until it's temperature drops below the melting point. It then becomes solid when the molecules are set in a highly organized structure. Simply that glass is another state of matter that is neither liquid nor solid. 

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And it is wrong to say supercooled liquid. Rather say Amorphous solid. Yes, it is solid, as you can see, glass doesn't have the 'perfect' shape, and as a result, not all molecules are connecting. Glass is not a slow-moving liquid. It is a solid, albeit an odd one. It is called an amorphous solid because it lacks the ordered molecular structure of true solids, and yet its irregular structure is too rigid for it to qualify as a liquid.

Glass sets in s more disorganized structure, making it an amorphous solid. The molecules can still move but do so extremely slowly. So slow that several hundreds of years aren't long enough to make a visible change. An old glass window with a thicker bottom was made that way.