packet vs mail boat

packet and mail boat both are nouns.

Word	Noun	Adjective	Verb	Adverb
packet	Yes	No	No	No
mail boat	Yes	No	No	No

As nouns, packet and mail boat are synonyms defined as:

Other synonyms of packet include mailboat, packet boat.

packet (noun)	mail boat (noun)
a small package or bundle	a boat for carrying mail
a boat for carrying mail
(computer science) a message or message fragment
a collection of things wrapped or boxed together