Also found in: Legal.
expatiate on (someone or something)
To speak or write about someone or something at length. Don't ask Uncle Harry about his collection of antique binoculars unless you want to hear him expatiate on it for hours on end.
expatiate on someone or something
to say or write many words about someone or something. She expatiated endlessly on the evils of tobacco. I have heard you expatiate on Harry quite enough, thank you.