ObsidionalOb*sid"i*o*nal\, a. [L. obsidionalis, from obsidio a siege, obsidere to besiege: cf.F. obsidional. See Obsess.] 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.