Glassbound is the term for a dragon that has, either willfully or by force or threat, shapeshifted down to a size small enough to be forced into a glass bottle which is then corked.
At these extremely small sizes, a dragon will not starve to death for centuries. However, the dragon will lose the strength to remove the cork or shatter the bottle, and because of glass's tendency to impede the flow of magic, a dragon will be incapable of gathering the magic power to teleport outside of the bottle.
To be glassbound by a sape is a deeply humiliating experience for a dragon. Many of the dragons that have rampaged and destroyed cities were once glassbound, with Takvedal being a notable example.
Retaliation against a dragon that is rampaging after a time glassbound is illegal by international law, as interfering with such a rampage would risk an attack from Feyndraig.