body armor vs coat of mail

body armor and coat of mail both are nouns.

Word	Noun	Adjective	Verb	Adverb
body armor	Yes	No	No	No
coat of mail	Yes	No	No	No

As nouns, body armor and coat of mail are synonyms defined as:

body armor and coat of mail: armor that protects the wearer's whole body

Other synonyms of body armor include body armour, cataphract, suit of armor, suit of armour.

body armor (noun)	coat of mail (noun)
armor that protects the wearer's whole body	armor that protects the wearer's whole body