Transformers as Inductors (Weird Results)
Shorting one winding and measuring the other gives you the leakage inductance, which is a result of imperfect coupling between the two windings, and is a function of the physical construction of the transformer.

Depending on your needs, it can have a practical application - zero voltage switching full-bridge converters often use the leakage inductance of the transformer to assist with the ZVS transitioning of the primary MOSFETs - but in general, transformers are designed to minimize this parameter by a variety of means (winding interleaving, etc.)