What kind of definition is a definition based on a Turing-test?

Question

Given that an extensional definition is one that defines the definienda by enumerating (partially or exhaustively) examples that belong to it (i.e. the list defines the concept), and intensional is a definition if it focuses on the principles behind the definienda, i.e. necessary and sufficient conditions, and therefire lists things that comply to these conditions as belonging to the given definition (i.e. rules define the concept), then which of these a Turing-test-like definition belongs to?

For those who are not familiar with the Turing test: it is a phenomenological test to overcome an indistinguishability-problem, by passing the decision to an objective judge. In this way it selects those entities that comply to a certain concept (the definition) in an indirect way. To put it simply, if a human judge cannot distinguish a computer from another human by interacting with them then we can take both the computer and the human as "intelligent" entities. Similarly, if a biological cellullar organism does not distinguish between a natural and an artificial cell (e.g. binds to both), than we might want to call both natural and artificial cells "living" (or not, but this is not the point here).

Irrespective of the fact whether such a definition is useful or not, I want to know what kind of definition is a Turing definition. It seems extensional, as on the one hand it practically distinguishes between entities whether they belong or not to the same set. Though on the other hand it relies on implicit (and unknown) principles, conditions, that control whether an entity belongs to the set or not, which might render it intensional. Furthermore, it is not enumerative in any sense, as it does not define the definienda by listing examples.

One might even think it is a third type of definition.

Answer 1

It's closest to an operational definition. The idea of such definitions is to identify empirical criteria that would provide every reason to believe that we are before an instance of F, and propose such criteria as the definition of F. Other operational definitions are the phenetic concept of biological species, or verificationism about meaning.

In general, operational definitions are discredited in philosophy: they stem from very extremely empiricist positions in epistemology that are nowadays generally considered as misguided. Operational definitions hope to find an empirically salient symptom of the definiendum whose presence coincide perfectly with it. But symptoms are hardly ever necessary, or sufficient. In the case that interests you, it appears both that a judge could mistake a cleverly built (but dumb) automaton for an intelligent agent, and an intelligent (but, say, shy) agent for a dumb automaton.

That doesn't mean they are useless, though: operational definitions might not be great qua definitions, but they provide a good empirical foothold for the investigation of the putative definiendum.