A star cruiser was a type of large interstellar spaceship with offensive/defensive armament. This descriptive term was applied to Federation starships and was a synonym for cruiser.
Both the starships USS Valiant and USS Enterprise were classified by the Eminian High Council in 2267 as star cruisers. (TOS: "A Taste of Armageddon")
Less than a century later, the Zakdorn strategist Sirna Kolrami called the USS Hathaway a star cruiser. (TNG: "Peak Performance")