The Collaborative International Dictionary of English v.0.48:

glitch \glitch\ n.
   1. A fault or defect in a system, plan, or machine.

   Syn: bug.
        [WordNet 1.5]

   2. (Elect.) A brief surge or interruption in the voltage in
      an electrical circuit or device.
      [PJC]

WordNet (r) 3.0 (2006):

glitch
    n 1: a fault or defect in a computer program, system, or machine
         [syn: bug, glitch]

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

glitch
 /glich/

    [very common; from German ?glitschig? slippery, via Yiddish ?glitshen?, to
    slide or skid]

    1. n. A sudden interruption in electric service, sanity, continuity, or
    program function. Sometimes recoverable. An interruption in electric
    service is specifically called a power glitch (also power hit), of grave
    concern because it usually crashes all the computers. In jargon, though, a
    hacker who got to the middle of a sentence and then forgot how he or she
    intended to complete it might say, ?Sorry, I just glitched?.

    2. vi. To commit a glitch. See gritch.

    3. vt. [Stanford] To scroll a display screen, esp. several lines at a time.
    WAITS terminals used to do this in order to avoid continuous scrolling,
    which is distracting to the eye.

    4. obs. Same as magic cookie, sense 2.

    All these uses of glitch derive from the specific technical meaning the
    term has in the electronic hardware world, where it is now techspeak. A
    glitch can occur when the inputs of a circuit change, and the outputs
    change to some random value for some very brief time before they settle
    down to the correct value. If another circuit inspects the output at just
    the wrong time, reading the random value, the results can be very wrong and
    very hard to debug (a glitch is one of many causes of electronic heisenbug
    s).

    [73-06-04]

    Coping with a hydraulic glitch.


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

glitch

   /glich/ [German "glitschen" to slip, via Yiddish "glitshen",
   to slide or skid] 1. (Electronics) When the inputs of a
   circuit change, and the outputs change to some random value
   for some very brief time before they settle down to the
   correct value.  If another circuit inspects the output at just
   the wrong time, reading the random value, the results can be
   very wrong and very hard to debug (a glitch is one of many
   causes of electronic heisenbugs).

   2. A sudden interruption in electric service, sanity,
   continuity, or program function.  Sometimes recoverable.  An
   interruption in electric service is specifically called a
   "power glitch" (or power hit), of grave concern because it
   usually crashes all the computers.  See also gritch.

   2. [Stanford] To scroll a display screen, especially several
   lines at a time.  WAITS terminals used to do this in order
   to avoid continuous scrolling, which is distracting to the
   eye.

   4. Obsolete.  Same as magic cookie.

   [Jargon File]