Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
1. quā̆drŭplātor (quadrĭplātor, Fest. p. 259 Müll. v. h. v.: quădrŭpŭlā-tor, Plaut. Pers. 1, 2, 18), ōris, m. [quadruplo].
2. quā̆drū̆plātor (quā̆drī̆-), ōris, m. [quadruplor], a public informer, who received a fourth part of the thing informed against (acc. to others, against one who committed an offence punishable with a fourfold penalty; cf. sector); also, in gen., a trickster, chicaner, Plaut. Pers. 1, 2, 18: deterrimus, Cic. Verr. 2, 2, 7, § 21; 2, 2, 8, § 22; Liv. 3, 72; cf. Paul. ex Fest. p. 259, 3 Müll.; Cic. Div. in Caecil. 7, 24; 21, 68.