Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
sēmuncĭārĭus, a, um, adj. [semuncia], amounting to a half-ounce (one twentyfourth of an as): semunciarium tantum ex unciario faenus factum, one twenty-fourth of an as upon each as, for a year of ten months, or, acc. to our mode of computation, five per cent. for a full year, Liv. 7, 27, 3; cf. id. 7, 16, 1: asses, weighing half an ounce, Plin. 33, 3, 13, § 46 Jahn.