warship vs combat ship

warship and combat ship both are nouns.

Word	Noun	Adjective	Verb	Adverb
warship	Yes	No	No	No
combat ship	Yes	No	No	No

As nouns, warship and combat ship are synonyms defined as:

warship and combat ship: a government ship that is available for waging war

Other synonyms of warship include war vessel.

warship (noun)	combat ship (noun)
a government ship that is available for waging war	a government ship that is available for waging war