Webster's Revised Unabridged Dictionary · 1913

Underworld

Underworld , noun

1.
The lower of inferior world; the world which is under the heavens; the earth.
That overspreads (with such a reverence) This underworld. — Daniel
2.
The mythological place of departed souls; Hades.
3.
The portion of the world which is below the horizon; the opposite side of the world; the antipodes. [Rare]
Fresh as the first beam glittering on a sail, That brings our friends up from the underworld. — Tennyson
4.
The inferior part of mankind. [Rare] — Atterbury