What is of or pertaining to a siege. Obsidional crown (Rom.Antiq.), a crown bestowed upon a general who raised the siege of a beleaguered place, or upon one who held out against a siege called?

obsidional — Of or pertaining to a siege. Obsidional crown (Rom.Antiq.), a crown bestowed upon a general who raised the siege of a beleaguered place, or upon one who held out against a siege. (Webster's 1913.)

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