Webster's Revised Unabridged Dictionary · 1913

Expanse

Expanse , noun

[From Latin expansus, past participle of expandere. See Expand.]

That which is expanded or spread out; a wide extent of space or body; especially, the arch of the sky.
The green expanse. — Savage
Lights... high in the expanse of heaven. — Milton
The smooth expanse of crystal lakes. — Pope

Expanse , transitive verb

To expand. [Obsolete]
That lies expansed unto the eyes of all. — Sir. T. Browne