disk (or CD-ROM) used to start the computer. It is often used when an operating system is corrupted or a hard drive crashes thus preventing the computer from being started up. (Also called system disk.)
A floppy disk that contains the information that is necessary to start the computer when the hard drive is not functioning properly.
a bootable disk that includes diagnostic and repair utilities, such as extract
a floppy disk that contains copies of the key files that your PC needs to start up
a floppy disk that you can use to boot your system if you're unable to start Windows
a tool that will start your computer from the floppy drive if the hard drive will not start
A CD-ROM or floppy disk that can be used to start the computer if the hard drive is not working properly.
The disk that contains the system files that your computer needs in order to operate. It is usually a hard disk inside your computer.
A boot disk, also known as a system disk or startup disk, is a floppy disk that has a copy of the files needed to start up your computer. When you start your computer from a boot disk, the operating system runs from the disk and not from the hard drive. A boot disk can be useful as a back-up if your hard drive's boot process becomes damaged by a virus. You may be able to avoid reformatting your hard drive by starting the computer with the boot disk and reloading the boot files onto your computer. Source: TechSoup.org
the disk whose System Folder is used when you Start your Mac