plate armour vs armour plate

plate armour and armour plate both are nouns.

Word	Noun	Adjective	Verb	Adverb
plate armour	Yes	No	No	No
armour plate	Yes	No	No	No

As nouns, plate armour and armour plate are synonyms defined as:

plate armour and armour plate: specially hardened steel plate used to protect fortifications or vehicles from enemy fire

Other synonyms of plate armour include armor plate, armor plating, plate armor.

plate armour (noun)	armour plate (noun)
specially hardened steel plate used to protect fortifications or vehicles from enemy fire	specially hardened steel plate used to protect fortifications or vehicles from enemy fire
a historical type of personal armor made from iron or steel plates, which superseded mail during the 14th century.