Make bulletproof.

Without flaws or loopholes:
— A bulletproof argument.

synonyms: unassailable, unshakable, watertight.

Roget 717: defending etc. v.; defensive; mural^†; armed, armed at all points, armed cap-a-pie, armed to the teeth; panoplied^†; iron-plated, ironclad; loopholed, castellated, machicolated^†, casemated^†; defended etc. v.; proof against.    armored, ballproof^†, bulletproof; hardened.    ... show more

Not penetrable by bullets.

Polish: kuloodporny