Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
dŭŏ-dē-vīcēsĭmus (or viges-), a, um, ordin. num., the eighteenth, Cato and Varr. ap. Non. 100, 11 sq.: pars tauri, Plin. 2, 73, 75, § 184; Plin. Ep. 6, 20, 5; and, per tmesin: duo enim devicesima Olympiade, Plin. 35, 8, 34, § 55.