plate armour vs armor plate

plate armour and armor plate both are nouns.

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

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

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

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

plate armour (noun)	armor 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a historical type of personal armor made from iron or steel plates, which superseded mail during the 14th century.