Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
ămāsĭus, ii, m. [amo], a lover (syn. amator), Plaut. Truc. 3, 1, 13; id. Cas. 3, 3, 27; Gell. 7, 8; 19, 9.