> To move about freely or at a will
> To speak or write at length or in detail
The Latin antecedent of “expatiate” is “exspatiari, which combines the prefix ex– (“out of“) with “spatiari” (“to take a walk“), itself from “spatium” (“space” or “course“).
Example
The naturalist is known for her willingness to expatiate on any number of issues relating to wildlife and the environment
During his book signing, he will expatiate on his military adventures.
A long-winded talker, he can expatiate on any topic