:block transfer computations: [from the television series
"Dr. Who"] n. Computations so fiendishly subtle and complex
that they could not be performed by machines. Used to refer to any
task that should be expressible as an algorithm in theory, but
isn't.
-- The AI Hackers Dictionary
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....