This adjective describes what belongs beneath the earth's surface, often referring to the realm of the dead or chthonic deities. Philippians 2:10 declares that at Jesus' name every knee should bow, 'in heaven and on earth and under the earth.' The genitive plural substantive refers to beings in the underworld realm. Classical usage shows this word for Pluto, chthonic gods, and the dead (Di Manes in Latin). Paul's cosmic triad (heavenly, earthly, subterranean) encompasses all realms of existence. The 'under-earth ones' may be the dead, demonic powers, or all sub-terrestrial beings who must acknowledge Christ's lordship.