breastplate vs egis

breastplate and egis both are nouns.

Word	Noun	Adjective	Verb	Adverb
breastplate	Yes	No	No	No
egis	Yes	No	No	No

As nouns, breastplate and egis are synonyms defined as:

breastplate and egis: armor plate that protects the chest; the front part of a cuirass

Other synonyms of breastplate include aegis.

breastplate (noun)	egis (noun)
armor plate that protects the chest; the front part of a cuirass	armor plate that protects the chest; the front part of a cuirass