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

runes
 pl.n.

    1. Anything that requires heavy wizardry or black art to parse: core
    dumps, JCL commands, APL, or code in a language you haven't a clue how to
    read. Not quite as bad as line noise, but close. Compare casting the
    runes, Great Runes.

    2. Special display characters (for example, the high-half graphics on an
    IBM PC).

    3. [borderline techspeak] 16-bit characters from the Unicode multilingual
    character set.


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

runes

   1. Anything that requires heavy wizardry or black art to
   parse: core dumps, JCL commands, APL or code in a
   language you haven't a clue how to read.  Not quite as bad as
   line noise, but close.

   Compare casting the runes, Great Runes.

   2. Special display characters (for example, the high-half
   graphics on an IBM PC).

   [Jargon File]