subterranean
adjective/ˌsʌbtəˈreɪniən/
Frequency rank: #11,661 of 20,003 in the WORDED list (wordfreq data)
Meaning
existing or situated underground.

Example sentence
The explorers discovered subterranean caves beneath the old city that had been hidden for centuries.
Synonyms & related words
More words in ranks 11,601–11,700
- spouta tube or lip through which liquid is poured or discharged.
- sproutto begin to grow or develop; to produce new shoots or buds.
- stencha strong and very unpleasant smell.
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- subsistenceThe minimum resources needed to maintain life; a way of living with only basic necessities.
- superhumanhaving abilities or qualities that exceed normal human limits.
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- tenacityThe quality of being very determined and not giving up.
- tolerableable to be accepted or endured; not too bad
- trespassto enter someone's land or property without permission.