plate armor vs armor plate

plate armor and armor plate both are nouns.

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

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

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

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

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a historical type of personal armor made from iron or steel plates, which superseded mail during the 14th century.