How Do I Reject A Disx From The MAc

I Was Burn A Movie On The Disc And There Was An Error Or Something Because I Can't Eject It I Tried Everything I Pressed F12 I Pressed The Eject Button On The Keyboard I Can't Drag The Disc Image To The Trash And Eject That Way I Restarted It Held Down The Mouse Button I Even Went To Terminal And Now I'm Now Trying Disk Utility And Says Every Time Try To Eject It The disk “PIONEER DVD-RW DVR-K06A” could not be unmounted.

Make sure that all applications and files are closed on this disk." What Does This Mean And Am I Doing Wrong