Webster’s Revised Unabridged Dictionary · 1913
Expanse
Ex·panse′ (ĕks·păns′), n. [From L. expansus, p. p. 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.
Ex·panse′, v. t. To expand. [Obs.]
That lies expansed unto the eyes of all. Sir. T. Browne.