speak or write in detail
expatiate - expand
The formal word ‘expatiate’ means to enlarge or expand upon something, such as an idea, theme, or topic, at length or in great detail. This can be done in writing or speech and the purpose is typically to make what you are trying to express as clear as possible. However, this term can also be used in a negative context if somebody feels that you are pontificating. Often followed by ‘on’ or ‘upon’.
As it stands, your report is simply not detailed enough. I need you to expatiate on the themes you are discussing.
Due to the current precarious economic climate, our recent meetings have involved considerable expatiation over the future direction of the company.
The celebrity’s eagerness to expatiate on political issues of which she has little understanding is a cause of contention for some.