A power management mode that conserves power by powering down the system. In hibernate mode the current state of the system is saved to the hard drive, and the system will power down. When a user turns the system power back on, the saved information is read from the hard disk, restoring the last used settings. Hibernate mode is similar to sleep mode, however in sleep mode the power cannot be shut off.
See also “Getting Started With Green IT” in Webopedia’s Did You Know? section.