Actually: An underground chamber with access only from the top . (18th Century)

Modern Slang: Asshole
Fold that into a tiny piece and shove them in your oubliette.
by Walter Street August 31, 2017
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A place you put someone to forget about them
Hoggle: “This is an oubliette. Labyrinth's full of 'em.”
Sarah: “Really... I didn’t know that”
Hoggle: “Oh, don't sound so smart! You don't even know what an oubliette is.”
by cornelios August 15, 2018
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