We don't have synonyms for armour plate yet — it may be a rare, specialized, newly coined, or misspelled word. The closest thesaurus entries we have are armor plate, armour plated and armour plates.
(n) :
Alternative spelling of armor plate. [(countable) A plate made of a tough material designed to withstand impact from a bullet, sharp instrument, etc., especially one worn on the body.]
(n) :
Alternative spelling of armor plate. [(countable) A plate made of a tough material designed to withstand impact from a bullet, sharp instrument, etc., especially one worn on the body.]