ship's boat vs gig

ship's boat and gig both are nouns.

Word	Noun	Adjective	Verb	Adverb
ship's boat	Yes	No	No	No
gig	Yes	No	No	No

As nouns, gig is a hyponym of ship's boat; that is, gig is a word with a more specific, narrower meaning than ship's boat:

ship's boat (noun)	gig (noun)
a boat for communication between ship and shore	a booking for musicians
	small two-wheeled horse-drawn carriage; with two seats and no hood
	tender that is a light ship's boat; often for personal use of captain
	long and light rowing boat; especially for racing
	an implement with a shaft and barbed point used for catching fish
	a cluster of hooks (without barbs) that is drawn through a school of fish to hook their bodies; used when fish are not biting