cruiser vs war vessel

cruiser and war vessel both are nouns.

Word	Noun	Adjective	Verb	Adverb
cruiser	Yes	No	No	No
war vessel	Yes	No	No	No

As nouns, war vessel is a hypernym of cruiser; that is, war vessel is a word with a broader meaning than cruiser:

cruiser: a large fast warship; smaller than a battleship and larger than a destroyer
war vessel: a government ship that is available for waging war

Other hypernyms of cruiser include combat ship, warship.

cruiser (noun)	war vessel (noun)
a large fast warship; smaller than a battleship and larger than a destroyer	a government ship that is available for waging war
a large motorboat that has a cabin and plumbing and other conveniences necessary for living on board
a car in which policemen cruise the streets; equipped with radiotelephonic communications to headquarters