Lewis & Short

portōrĭum (dat. plur. PORTORIEIS, Plebisc. Thermens ap. Orell. 3673), ĭi, n. [root por, whence porto, portitor, portus, that belongs to carrying or conveying; hence],

  1. I. A tax, toll, duty, impost paid on goods imported or exported: portorium dare, Lucil. ap. Non. 37, 20; Cic. Verr. 2, 2, 72, § 176; 2, 2, 75, § 185; id. Font. 5, 19; id. Pis. 36, 87; Caes. B. G. 1, 18; 3, 1; Liv. 39, 24; Plaut. Trin. 4, 4, 15; Caecil. ap. Gell. 15, 14, 5; Dig. 19, 2, 60 fin.; cf.: ego pol istum portitorem privabo portorio, Plaut. As. 1, 3, 7: portorium circumvectionis, a tax paid for the right of hawking goods about the country, a peddler’s tax, Cic. Att. 2, 16, 4.
  2. * II. Fare, freight, = naulum: Charon expetens portorium, App. M. 6, p. 180, 28.