We don't have synonyms for grand-guard yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are grand guard.
(n) :
Alternative form of grand guard. [(historical) A piece of plate armor protecting one shoulder, side of the chest, and side of the neck (typically the left), during jousting, augmenting or replacing a pauldron.]
(n) :
Alternative form of grand guard. [(historical) A piece of plate armor protecting one shoulder, side of the chest, and side of the neck (typically the left), during jousting, augmenting or replacing a pauldron.]