What is Actio Publiciana?

Legal Definition
An action which lay for one who had lost a thing of which he had bona fide obtained possession. before he had gained a property in it, in older to have it restored, under color that he had obtained a property in it by prescription. Inst 4, 6k 4; Heinecc. Elem. lib. 4, tit. 6, § 1131; Hallifax, Anal. b. 3, c. 1, n. 9. It was an honorary action, and derived its name from the praetor Publicius, by whose edict it was first given. Inst. 4, 6, 4.
-- Black's Law Dictionary