I. -nēən, -nyən adjective
or sub·ter·ra·ne·ous -nēəs
Etymology: subterranean from Latin subterrane us underground, subterranean + English -an; subterraneous from Latin subterraneus, from sub- + -terraneus (from terra ground, earth + -aneus, from -anus -an) — more at terrace
1. : being or lying under the surface of the earth : situated in the earth or underground
subterranean springs
— opposed to surficial
2.
a. : functioning, operating, or suitable for operating beneath the surface of the earth
b. : existing or working in secret : hidden
• sub·ter·ra·nean·ly adverb
II. noun
( -s )
Etymology: Latin subterrane us + English -an (n. suffix)
1. : one who lives, develops, or works underground
2. : an underground cave or room : cavern