The Collaborative International Dictionary
Souterrain \Sou"ter*rain\, n. [F. See Subterranean.]
A grotto or cavern under ground. [Obs.]
--Arbuthnot.
Wiktionary
n. (context archaeology English) An underground chamber or passage sometimes used as a store, especially one associated with Iron Age settlements.
Wikipedia
Souterrain (from French sous terrain, meaning "under ground") is a name given by archaeologists to a type of underground structure associated mainly with the European Atlantic Iron Age.
These structures appear to have been brought northwards from Gaul during the late Iron Age. Regional names include earth houses, fogous and Pictish houses. The term souterrain has been used as a distinct term from fogou meaning ‘cave’. In Cornwall the regional name of fogou ( Cornish for ‘cave’) is applied to souterrain structures. The design of underground structures has been shown to differ among regions; for example, in western Cornwall the design and function of the fogou appears to correlate with a larder use.
Usage examples of "souterrain".
The Picts of the Pictish period, in eastern Scotland, lived in souterrains, in small villages.
Thence returning along the coast by Savona, Noli, Albenga, Oneglia, Monaco, Nice, Antibes, Frejus, Aix, Marseilles, Avignon, Nismes, Montpellier, Frontignan, Cette, Agde, and along the canal of Languedoc, by Bezieres, Narbonne, Cascassonne, Castelnaudari, thro' the Souterrain of St.