Ensure Part 09 is the same size as Parts 01-08. If it's significantly smaller (and isn't the last part), the download likely timed out. Ensure Part 09 is the same size as Parts 01-08

If you need to describe this file for a post or a directory listing, What is "Battlefield.Hardline.part09.rar"?

It sounds like you're dealing with a multi-part archive for . Specifically, "part09.rar" is just one slice of a larger set of compressed files required to install or extract the game. Since this is a technical file component, What is "Battlefield.Hardline.part09.rar"?