Definitions

1. noun

a cave or other opening in the earth, especially one used as a dwelling place

“The subterrane was hidden deep beneath the earth’s surface, accessible only by a secret entrance.”

2. adjective

relating to or situated beneath the earth’s surface

“The subterrane architecture of the ancient city was a marvel of its time.”

3. adverb

beneath the earth’s surface

“The subterrane tunnels stretched for miles beneath the city’s streets.”