What is "rough idea"? What is the opposite word for this?

Rebecca

A "rough idea" means a very vague or general idea of what something is about. If you have a "rough idea", you know have a guess of what something is about, but you don't have all the details yet. The opposite of this phrase is a "clear idea". If you have a clear idea, you know nearly all the details about something and you know exactly what it is about. Ex: I have a rough idea of what the test is going to look like, but I still don't know how to prepare.