The Collaborative International Dictionary
Vallar crown
Vallar \Val"lar\, a. [L. vallaris.] Of or pertaining to a rampart.
Vallar crown (Rom. Antiq.), a circular gold crown with palisades, bestowed upon the soldier who first surmounted the rampart and broke into the enemy's camp.
Wiktionary
vallar crown
n. (context historical Roman antiquity English) A circular gold crown with palisades, bestowed upon the soldier who first surmounted the rampart and broke into the enemy's camp.