adj.
Pronunciation: ˌ s ə b-t ə - ' r ā -n ē - ə n, -ny ə n
Variant: also sub · ter · ra · neous \ -n ē - ə s, -ny ə s \
Function: adjective
Etymology: Latin subterraneus, from sub- + terra earth ― more at THIRST
Date: 1603
1 : being, lying, or operating under the surface of the earth
2 : existing or working in secret : HIDDEN <a subterranean network of criminals>
– sub · ter · ra · nean · ly also sub · ter · ra · neous · ly adverb