Lewis & Short

ŏpīnātor, ōris, m. [opinor].

  1. * I. A supposer, conjecturer: ego vero ipse et magnus quidam sum opinator, etc., Cic. Ac. 2, 20, 66.
  2. II. Under the emperors, one who collected the tribute-corn in the provinces for the army, Cod. Just. 12, 38, 11; cf. Cod. Th. 7, 4, 26; 11, 7, 16.