Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
dōnātor, ōris, m. [dono], a giver, donor (post-Aug.; in the jurists very freq.), Dig. 42, 1, 49; Just. Inst. 2, 7, § 2; Cod. Just. 8, 54, 1 et saep.; Sen. Hippol. 1217.