ou·bli·ette (o?o?bl?-?t?)n. A dungeon with a trapdoor in the ceiling as its only means of entrance or exit.[French, from oublier, to forget, from Old French oblider, from Vulgar Latin *obl?t?re, from Latin obl?tus, past participle of obl?v?sc?; see lei- in Indo-European roots.]American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.oubliette (?u?bl???t) n (Architecture) a dungeon, the only entrance to which is through the top[C19: from French, from oublier to forget]Collins English Dictionary ? Complete and Unabridged, 12th Edition 2014 © HarperCollins Publishers 1991, 1994, 1998, 2000, 2003, 2006, 2007, 2009, 2011, 2014ou?bli?ette (?u bli??t) n. a secret dungeon with an opening only in the ceiling. [1810?20;