1) Invulnerable 2) Make safe against bombings 3) Shellproof 4) Used during air raids 1) Invulnerable 2) Safe 3) Shellproof 
• (n.) A structure which heavy shot and shell will not penetrate. • (a.) Secure against the explosive force of bombs.
Bomb'proof` adjective Secure against the explosive force of bombs. -- noun A structure which heavy shot and shell will not penetrate. 
[adj] - able to resist the explosive force of bombs and shells
bombproof 1. A chamber, or room, (often underground) reinforced against bombing and provided with food and living facilities; used during air raids. 2. Anything which is able to resist the explosive force of bombs and shells; such as, a bombproof shelter or vehicle.
shellproof adjective able to resist the explosive force of bombs and shells; `bombproof shelter`
strong enough to resist the impact and explosive force of bombs or shells: a bombproof shelter.
A hold or anchor that is thought to offer the utmost security; for example, a top-rope anchor around a large, stable tree trunk or immovable boulder.