Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
ŏb-ŏrĭor, ortus, 4, v. dep., to arise, appear, spring up (class.): oboritur, nascitur, nam praepositionem ob pro ad, solitam poni, testis hic versus: tantum gaudium oboriri ex tumultu maximo, Paul. ex Fest. p. 190 Müll.: tenebrae oboriuntur, Plaut. Curc. 2, 3, 30: lacrimis ita fatur obortis, Verg. A. 11, 41; Ov. M. 2, 181: bellum, Liv. 21, 8: laetitia, Ter. Heaut. 4, 3, 2: vide, quanta lux liberalitatis et sapientiae mihi apud te dicenti oboriatur, * Cic. Lig. 3, 6: sitis, Suet. Ner. 34: caligo, id. ib. 19 al.: verba, App. Flor. 1, p. 29 Oud.