verb (used without object), ex·pa·ti·at·ed, ex·pa·ti·at·ing.
1.
to enlarge in discourse or writing; be copious in description or discussion: to expatiate upon a theme.
2.
Archaic.to move or wander about intellectually, imaginatively, etc., without restraint.
Origin: 1530–40; < Latinexpatiātus past participle of ex(s)patiārī to wander, digress, equivalent to ex-ex-1 + spatiārī to walk about, derivative of spatiumspace; see -ate1
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.