Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
trītor, ōris, m. [tero], a rubber, grinder, chafer: colorum, a grinder of colors, Plin. 35, 11, 40, § 145: compedium, a chain-rubber, a term of reproach applied to a chained slave, Plaut. Pers. 3, 3, 15: stimulorum, of one who is often scourged, id. ib. 5, 2, 17: ARGENTARIVS, i. e. caelator, Inscr. Rein. cl. 11, n. 97.