Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
trĭbŭārĭus, a, um, adj. [tribus], of or belonging to a tribe or tribes: crimen sodalitiorum, i. e. a bribing of the tribes, Cic. Planc. 19, 47: res, id. ib. 15, 36.