subterrestrial

[ suhb-tuh-res-tree-uh l ]
/ ˌsʌb təˈrɛs tri əl /

adjective

underground; subterranean.

Origin of subterrestrial

First recorded in 1605–15; sub- + terrestrial
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019