- to enlarge in discourse or writing; be copious in description or discussion:to expatiate upon a theme.
- Archaic. to move or wander about intellectually, imaginatively, etc., without restraint.
1530s, "walk about, roam freely," from L. expatiatus, exspatiatus, pp. of expatiari, exspatiari "wander, digress," from ex- "out" + spatiari "to walk, spread out," from spatium (see space). Meaning "talk or write at length" is 1610s.
(http://dictionary.reference.com/browse/expatiate)
"When the baron expatiated upon the superior practices of Europe, the Indians were baffled."
- Charles Mann, 1491: New Revelations of the Americas Before Columbus