subterranean
sub-ter-ra-ne-an
adjective
Existing, occurring, or done beneath the earth's surface; underground.
"They discovered a vast subterranean network of tunnels."
Thesaurus
Synonyms: covert, ulterior, subterraneous, subsurface
sub-ter-ra-ne-an
Existing, occurring, or done beneath the earth's surface; underground.
"They discovered a vast subterranean network of tunnels."
Synonyms: covert, ulterior, subterraneous, subsurface