The Jargon File (version 4.4.7, 29 Dec 2003):

raw mode
 n.

    A mode that allows a program to transfer bits directly to or from an I/O
    device (or, under bogus operating systems that make a distinction, a disk
    file) without any processing, abstraction, or interpretation by the
    operating system. Compare rare mode, cooked mode. This is techspeak
    under Unix, jargon elsewhere.


The Free On-line Dictionary of Computing (30 December 2018):

raw mode

    A mode that allows a program to transfer
   bits directly to or from an I/O device without any
   processing, abstraction, or interpretation by the operating
   system.

   Systems that make this distinction for a disk file are
   generally regarded as broken.

   Compare rare mode, cooked mode.

   [Jargon File]

   (2002-04-14)