partition A portion of a hard disk that functions as a separate unit. A single hard disk can be divided into several partitions, each of which functions as a separate drive and has its own volume name (such as D:, E:, F:, and so on). The purpose is to make the drive more efficient, as the computer can search smaller sections for a specific file rather than the entire drive. The verb to partition refers to the process of dividing the hard drive into partitions.