WordNet (r) 3.0 (2006):

GIGO
    n 1: (computer science) a rule stating that the quality of the
         output is a function of the quality of the input; put
         garbage in and you get garbage out

V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):

GIGO
       Garbage In Garbage Out


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

GIGO
 /gi:?goh/

    1. ?Garbage In, Garbage Out? ? usually said in response to lusers who
    complain that a program didn't ?do the right thing? when given imperfect
    input or otherwise mistreated in some way. Also commonly used to describe
    failures in human decision making due to faulty, incomplete, or imprecise
    data.

    2. Garbage In, Gospel Out: this more recent expansion is a sardonic comment
    on the tendency human beings have to put excessive trust in ?computerized?
    data.


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

Garbage In, Garbage Out
GIGO

    (GIGO) /gi:'goh/ Wilf Hey's maxim expressing the
   fact that computers, unlike humans, will unquestioningly
   process nonsensical input data and produce nonsensical output.
   Of course a properly written program will reject input data
   that is obviously erroneous but such checking is not always
   easy to specify and is tedious to write.

   GIGO is usually said in response to lusers who complain that
   a program didn't "do the right thing" when given imperfect
   input or otherwise mistreated in some way.  Also commonly used
   to describe failures in human decision making due to faulty,
   incomplete, or imprecise data.

   The expansion "Garbage In, Gospel Out" is an ironic comment on
   the tendency to put excessive trust in "computerised" data.

   [Jargon File]

   (2004-10-03)