Definition of "vasty"

I can call spirits from the vasty deep.

c. 1597 (date written), William Shakespeare, “The First Part of Henry the Fourth, […]”, in Mr. William Shakespeares Comedies, Histories, & Tragedies […] (First Folio), London: […] Isaac Iaggard, and Ed[ward] Blount, published 1623, [Act III, scene i]

[…] the pattern of life it offers has a homely grace. It reminds you of a placid rivulet, meandering smoothly through green pastures and shaded by pleasant trees, till at last it falls into the vasty sea; […]

1919, W[illiam] Somerset Maugham, “chapter 7”, in The Moon and Sixpence, [New York, N.Y.]: Grosset & Dunlap Publishers […]