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

Turing tar-pit
 n.

    1. A place where anything is possible but nothing of interest is practical.
    Alan Turing helped lay the foundations of computer science by showing that
    all machines and languages capable of expressing a certain very primitive
    set of operations are logically equivalent in the kinds of computations
    they can carry out, and in principle have capabilities that differ only in
    speed from those of the most powerful and elegantly designed computers.
    However, no machine or language exactly matching Turing's primitive set has
    ever been built (other than possibly as a classroom exercise), because it
    would be horribly slow and far too painful to use. A Turing tar-pit is any
    computer language or other tool that shares this property. That is, it's
    theoretically universal ? but in practice, the harder you struggle to get
    any real work done, the deeper its inadequacies suck you in. Compare 
    bondage-and-discipline language.

    2. The perennial holy wars over whether language A or B is the ?most
    powerful?.


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

Turing tar-pit

   A place where anything is possible but nothing of interest is
   practical.  Alan M. Turing helped lay the foundations of
   computer science by showing that all machines and languages
   capable of expressing a certain very primitive set of
   operations are logically equivalent in the kinds of
   computations they can carry out, and in principle have
   capabilities that differ only in speed from those of the most
   powerful and elegantly designed computers.  However, no
   machine or language exactly matching Turing's primitive set
   has ever been built (other than possibly as a classroom
   exercise), because it would be horribly slow and far too
   painful to use.

   A "Turing tar-pit" is any computer language or other tool that
   shares this property.  That is, it's theoretically universal
   but in practice, the harder you struggle to get any real work
   done, the deeper its inadequacies suck you in.  Compare
   bondage-and-discipline language.

   A tar pit is a geological occurence where subterranean tar
   leaks to the surface, creating a large puddle (or pit) of tar.
   Animals wandering or falling in get stuck, being unable to
   extricate themselves from the tar.  La Brea, California, has a
   museum built around the fossilized remains of mammals and
   birds found in such a tar pit.

   [Jargon File]

   (1998-06-27)