Webster's Revised Unabridged Dictionary · 1913

Expatiate

Expatiate , intransitive verb

[Latin expatiatus, exspatiatus, past participle of expatiari, exspatiari, to expatiate; ex out + spatiari to walk about spread out, from spatium space. See Space.]

1.
To range at large, or without restraint.
Bids his free soul expatiate in the skies. — Pope
2.
To enlarge in discourse or writing; to be copious in argument or discussion; to descant.
He expatiated on the inconveniences of trade. — Addison

Expatiate , transitive verb

To expand; to spread; to extend; to diffuse; to broaden.
Afford art an ample field in which to expatiate itself. — Dryden