Wiktionary
breakproof
a. Resistant to breaking; unbreakable.
Usage examples of "breakproof".
The machine that broke the breakproof restrictor that is built into every robot or android since time began.
The most easily swiped things, like the prayer fans and the blood diamonds and the fire pearls, were kept behind tough, breakproof glass.
The breakproof plastic shattered nicely, leaving her holding a jagged shard attached to the handle.