body armour vs cataphract

body armour and cataphract both are nouns.

Word	Noun	Adjective	Verb	Adverb
body armour	Yes	No	No	No
cataphract	Yes	No	No	No

As nouns, body armour and cataphract are synonyms defined as:

Other synonyms of body armour include body armor, coat of mail, suit of armor, suit of armour.

body armour (noun)	cataphract (noun)
armor that protects the wearer's whole body	armor that protects the wearer's whole body