packet boat vs boat

packet boat and boat both are nouns.

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

As nouns, boat is a hypernym of packet boat; that is, boat is a word with a broader meaning than packet boat:

packet boat (noun)	boat (noun)
a boat for carrying mail	a small vessel for travel on water
	a dish (often boat-shaped) for serving gravy or sauce

packet boat (verb)	boat (verb)
	ride in a boat on water