What is Actio In Factum?

Legal Definition
An action adapted to the particular case, having an analogy to some actio in jus, the latter being founded on some subsisting acknowledged law. Spence, Eq. Jur. 212. The origin of these actions is similar to that of actions on the case at common law.
-- Black's Law Dictionary
Legal Definition
A Roman law action similar to an action on the case at common law.
-- Ballentine's Law Dictionary