-proof /pruːf/ BrE AmE suffix
1 . [in adjectives] used to describe something which a particular thing cannot harm or pass through, or which protects people against that thing:
a bulletproof car
a waterproof jacket
an ovenproof dish (=that cannot be harmed by heat)
2 . [in adjectives] used to describe something which cannot easily be affected or damaged by someone or something:
a childproof container
vandal-proof
3 . [in verbs] to treat or make something so that a particular thing cannot harm it or pass through it, or so that it gives protection against it:
soundproof a room (=so that sound cannot get into or out of it)