What is Actio Utilis?

Legal Definition
A beneficial action or equitable action. An action founded on equity instead of strict law, and available for those who had equitable rights or the beneficial ownership of property. Actions are divided into directed or utiles actions. The former are founded on certain legal obligations which from their origin were accurately defined and recognized as actionable. The latter were formed analogically in imitation of the former. They were permitted in legal obligations for which the actiones directoe were not originally intended, but which resembled the legal obligations which formed the basis of the direct action. Mackeld. Rom. Law, § 207.
-- Black's Law Dictionary
Legal Definition
An action brought by the holder of the legal title in behalf of the beneficiary thereof.
-- Ballentine's Law Dictionary