expatiate

verb

1. To write or speak at length; to be copious in argument or discussion.

   “[H]e expatiated on the inconveniences of trade, that carried from us the commodities of our country, and made a parcel of upſtarts as rich as men of the moſt ancient families of England.”

   “To the pure mind of Isabella thought of no other had arisen; and it was far better that the generous romance of her young heart should expatiate on the rival in heaven, than for a moment dread a rival on earth, and therefore become subject to jealousy...”

   “Governor Bellingham, in a loose gown and easy cap,—such as elderly gentlemen loved to indue themselves with, in their domestic privacy,—walked foremost, and appeared to be showing off his estate, and expatiating on his projected improvements.”

   “Now, as the business of standing mast-heads, ashore or afloat, is a very ancient and interesting one, let us in some measure expatiate here.”

   “Wooster: If you ask me, art is responsible for most of the trouble in the world. / Jeeves: An interesting theory, sir. Would you care to expatiate upon it? / Wooster: As a matter of fact, no, Jeeves. The thought just occurred to me, as thoughts do. / Jeeves: Very good, sir.”

2. (rare)To range at large, or without restraint.

   “[L]ooks on heav'n with more than mortal eyes, / Bids his free ſoul expatiate in the skies, / Amidſt her kindred ſtars familiar roam, / Survey the region, and confeſs her home! Such was the life great Scipio once admir'd, / Thus Atticus, and Trumball thus retir'd.”

3. (obsolete)To expand; to spread; to extend; to diffuse; to broaden.