Lewis & Short

uncĭārĭus, a, um, adj. [uncia], of or belonging to a twelfth part, containing a twelfth: heres, i. e. who inherits a twelfth part, Dig. 30, 1, 34 fin.: fenus, i. e. one twelfth of the principal was returned annually as interest, or 8 1/3 per cent. (cf. Rein, Privatr. 630 sqq.; Marquardt, Röm. Alterth. 3, 2, 48); Tac. A. 6, 16; Liv. 7, 16, 1; 7, 27, 3: lex, i. e. de fenore unciario, Fest. p. 375: unciariā stipe collatā, i. e. of an as (weighing one ounce), from each person, Plin. 34, 5, 11, § 21: vitis, bearing grapes that weigh an ounce, Col. 3, 2, 2; cf. Isid. Orig. 17, 5, 17