Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
faenē̆bris (less correctly fēn-, foen-), e, adj. [faenus; cf. Paul. ex Fest. pp. 86 and 94], of or relating to interest or usury: leges, Liv. 35, 7: res, the matter of interest and debts, the relations between debtor and creditor, id. 7, 21: pecunia, lent on interest, Suet. Calig. 41: malum, Tac. 6, 16.
fēnē̆bris, fēnĕrārĭus, fēnĕror, etc., v. faenebris, faeneror, etc.