porthole vs embrasure

porthole and embrasure both are nouns.

Word	Noun	Adjective	Verb	Adverb
porthole	Yes	No	No	No
embrasure	Yes	No	No	No

As nouns, porthole and embrasure are synonyms defined as:

porthole and embrasure: an opening (in a wall or ship or armored vehicle) for firing through

Other synonyms of porthole include port.

porthole (noun)	embrasure (noun)
a window in a ship or airplane	an opening (in a wall or ship or armored vehicle) for firing through
an opening (in a wall or ship or armored vehicle) for firing through