infrangible
shatterproof
splinterless
splinterproof
irruptible
foolproof
immovable
impassable
impervious
impregnable
indestructible
indissoluble
insurmountable
inviolable
invulnerable
irrevocable
nonexistent
seamless
unassailable
unchangeable
unchanged
undefended
undetectable
uninhabitable
unscathed
unstoppable
valueless
weightless
breakable
unmistakable
unshakable
unshakeable
brittle