Military installation consisting of an underground structure where ballistic missiles can be stored and fired WordNet 3.0 & Open English WordNet

A missile launch facility, also known as an underground missile silo, launch facility, or nuclear silo, is a vertical cylindrical structure constructed underground, for the storage and launching of intercontinental ballistic missiles, intermediate-range ballistic missiles, medium-range ballistic missiles. Wikipedia

A structure used for launching ballistic missiles Wikipedia Disambiguation

Building that stores and launches missiles Wikidata

An underground bunker used to hold missiles which may be launched. Wiktionary

Underground bunker. Wiktionary (translation)