subterraneous

/ˌsʌbtəˈreɪniəs/
adjective
  1. Another form of subterranean; existing or happening under the earth's surface.
    • The explorers discovered a vast subterraneous lake deep in the cave.
    • The subterraneous tunnels were used for mining centuries ago.
    • Subterraneous fungi play an important role in forest ecosystems.
Antonyms
What does "subterraneous" mean? | whatsthatwordmean | whatsthatwordmean