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

gedanken
 /g@?dahn?kn/, adj.

    Ungrounded; impractical; not well-thought-out; untried; untested.

    ?Gedanken? is a German word for ?thought?. A thought experiment is one you
    carry out in your head. In physics, the term gedanken experiment is used to
    refer to an experiment that is impractical to carry out, but useful to
    consider because it can be reasoned about theoretically. (A classic
    gedanken experiment of relativity theory involves thinking about a man in
    an elevator accelerating through space.) Gedanken experiments are very
    useful in physics, but must be used with care. It's too easy to idealize
    away some important aspect of the real world in constructing the
    ?apparatus?.

    Among hackers, accordingly, the word has a pejorative connotation. It is
    typically used of a project, especially one in artificial intelligence
    research, that is written up in grand detail (typically as a Ph.D. thesis)
    without ever being implemented to any great extent. Such a project is
    usually perpetrated by people who aren't very good hackers or find
    programming distasteful or are just in a hurry. A gedanken thesis is
    usually marked by an obvious lack of intuition about what is programmable
    and what is not, and about what does and does not constitute a clear
    specification of an algorithm. See also AI-complete, DWIM.


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

Gedanken

   John Reynolds, 1970.  "GEDANKEN - A Simple Typeless Language
   Based on the Principle of Completeness and the Reference
   Concept", J.C.  Reynolds, CACM 13(5):308-319 (May 1970).

   [Jargon File]


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

gedanken

   /g*-dahn'kn/ Ungrounded; impractical; not well-thought-out;
   untried; untested.

   "Gedanken" is a German word for "thought".  A thought
   experiment is one you carry out in your head.  In physics, the
   term "gedanken experiment" is used to refer to an experiment
   that is impractical to carry out, but useful to consider
   because it can be reasoned about theoretically.  (A classic
   gedanken experiment of relativity theory involves thinking
   about a man in an elevator accelerating through space.)
   Gedanken experiments are very useful in physics, but must be
   used with care.  It's too easy to idealise away some important
   aspect of the real world in constructing the "apparatus".

   Among hackers, accordingly, the word has a pejorative
   connotation.  It is typically used of a project, especially
   one in artificial intelligence research, that is written up in
   grand detail (typically as a Ph.D.  thesis) without ever being
   implemented to any great extent.  Such a project is usually
   perpetrated by people who aren't very good hackers or find
   programming distasteful or are just in a hurry.  A "gedanken
   thesis" is usually marked by an obvious lack of intuition
   about what is programmable and what is not, and about what
   does and does not constitute a clear specification of an
   algorithm.  See also AI-complete, DWIM.