The Free On-line Dictionary of Computing (19 January 2023):

Extensible Firmware Interface
EFI

    (EFI) A specification originating from Intel
   Corporation, defining the interface between an operating
   system and platform firmware, and aiming to reduce OS
   dependence on details of the firmware implementation.

   EFI Home (http://intel.com/technology/efi/).

   (2004-10-23)