Not a sharp melting point, no. And it also depends on the grade of glass.
Unlike something such as, say, ice - which melts at 0 degrees C and then remains as a liquid with consistent physical properties until it reaches boiling point, glasses tend to soften and then gradually decrease in viscosity until they become more mobile fluids. The grade of glass is also important, as some will resist temperature much more than others.
A softening starting at around the 1500 - 1600 degrees C mark is common, with more workable liquid properties at around 1750 degrees C or so.