A penthouse was a type of apartment on the top floor of a building known for its luxury and high cost.
In 2024, B.C. sarcastically suggested that Benjamin Sisko and Michael Webb's "demands" during the Bell Riots might as well include a couple of silk shirts and a penthouse in Singapore. (DS9: "Past Tense, Part II")
According to D'Vana Tendi, deck 1 quarters on USS Cerritos were penthouse suites (i.e. luxurious and spacious). (LD: "Room for Growth")