One hearing the word luxury thinks of rich people and extravagant lifestyles that mere mortals can’t afford. Sometimes "luxury" can be subjective but when it comes to cruising, the standards are well-established. Luxury means a high fare (more than $500 per person, daily) and an exotic itinerary with amazing landscapes and elegant ports to visit.
Also, the means of transport are important, in this case the ships. Everything that could be found in a 5-star hotel must be also found in a luxury ship: jacuzzi, gym, restaurants, internet connection, conference room, bars, casinos, swimming pools, saunas, lounges and bedrooms with superb panoramas.
The way a ship looks on the inside adds value and glamour to luxury: decorations of good taste, elegant materials and real works of art signed by famous artists, for an extra touch of luxury. In this sense, some ships are really floating art museums, a delight for the passengers who take great interest in art.
What is also important to define a luxury ship is the privacy it can offer: if the deck is as crowded as a plaza in Milan at the peak of the touristic season, then luxury fades off. The few passengers must have the deck all for themselves for sunbathing, dolphin or whales watching etc.
Some cruise liners manage to offer free access to its passengers all over the ship or free cocktails and drinks all day long and famous wine with the meals.
Also during a luxury cruise the service must have the highest standards, the chef must prepare the most sophisticated meals, the staff should be very courteous and experienced. The cuisine is both international and regional (influenced by the itinerary of the ship).
Now that you have the luxury factors, you will know how to ask for in a dream cruise.