Refers to a vessel designed for pleasure cruising or a naval cruiser. Context determines whether it is a civilian cruise ship or a military cruiser.
Next summer vacation, we plan to travel the Mediterranean on a cruise ship.
The cruiser is equipped with the latest radar.
巡洋艦 is the standard term for a naval cruiser (warship). 巡航船 is less common in military contexts but can carry the same meaning.
Compound of 巡航 (cruising) and 船 (ship). The term is transparently derived from its components.