From Middle English obsidional, from Latin obsidiōnālis, from obsidiō (“siege, blockade”), from obsidēre (“beset, besiege, hem in”).

• IPA^(key): /əbˈsɪdɪənəl/

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• Hyphenation: ob‧si‧di‧on‧al

obsidional

1. Pertaining to a siege.
   • 1846–1847, Henry Edward Napier, “Miscellaneous Chapter for the Fifteenth Century”, in Florentine History, from the Earliest Authentic Records to the Accession of Ferdinand the Third, Grand Duke of Tuscany. In Six Volumes, volume IV, London: Edward Moxon, →OCLC, page 3:

     Nor was this strong geographical position her [Florence's] only bulwark; the capital itself in those unskilful days of obsidional tactics was deemed impregnable except through famine.

• obsidional coin
• obsidional crown

Learned borrowing from Latin obsidiōnālis.

• IPA^(key): /ɔp.si.djɔ.nal/

obsidional (feminine obsidionale, masculine plural obsidionaux, feminine plural obsidionales)

1. obsidional

   couronne obsidionale ― (please add an English translation of this usage example)

• “obsidional”, in Trésor de la langue française informatisé , 2012.