Some scientists say this:
Glass is an amorphous solid. A material is amorphous when it has no long-range order, that is, when there is no regularity in the arrangement of its molecular constituents on a scale larger than a few times the size of these groups. [...] A solid is a rigid material; it does not flow when it is subjected to moderate force.
Others state that glass is void of a crystalline structure and therefore is considered a liquid.
I believe it depends on what temperature we are talking about. Average glass melts completely at 1400-1600 degrees C. Some melt as low as 500 degrees C.
My kids says emphatically that it is in fact a liquid. I thought this was interesting.