An air-raid shelter, a structure designed to give protection against bombs.(noun)
Wiktionary.org : Text is available under the Creative Commons Attribution-ShareAlike License
Use "bomb shelter" in a sentence
"Kyle’s new apartment on the twenty-third floor of the Collier Foundation building was definitely a step up from the abandoned bomb shelter they had squatted in when the Movement had first returned to Seattle, shortly before the Great Leap Forward."
"And under that, a roomy bomb shelter that nobody knew about."