Definition - What does Interrogatory mean?
An interrogatory is a formal question that is asked within the context of an open case. More specifically, it is usually in written form and asks for clarification of a matter through requesting a specific question be answered by either party prior to furthering the case. Most interrogatories are done before the case is started in an effort to agree the specific facts of the case between both sides. It is a form of discovery and is in writing.
Justipedia explains Interrogatory
An interrogatory is usually requested by a solicitor or legal team and asked of the other side's legal team, who in turn ask their client (the plaintiff and the defendant in the case at hand) what they would say to the question, and then answer for them as best they can and in line with their response.