Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
oppessŭlātus (obp-), a, um, Part., from the obs. oppessulo [ob-pessulus], bolted or barred (post-class.): januam firmiter oppessulatam pulsare, App. M. 1, p. 112, 11: januae, Amm. 31, 13, 15.