Andre,
Your definition of "Black Tie" is basically correct. A gentleman's "formal" attire consists of a formal dress shirt (usualy with either pleated or ruffled front) with studs and cuff links, black formal dress pants (with satin stripes on the outside seams), black bow tie, cummerbund or vest, black socks, black dress shoes (well polished or patent leather, with leather soles), and a dinner jacket or waist coat. The jacket or waistcoat may be any color, but white and pastel shades are generally reserved for wear in warm weather of the summer season or the tropics.
Some common variations are quite acceiptable.
>> Contemporary fashion replaces the black bow tie with a bow tie of the same fabric as the vest or the cummerbund.
>> Bermudans frequently wear formal shorts, with the same satin stripe, and knee-high socks in place of the full length trowsers.
>> Scotsmen frequently wear a kilt in place of the trowsers. On my last cruise, I also saw a Scotsman wearing the plaid trousers of his clan in place of the standard formal trowsers.
>> Military and naval personnel of any nation on active duty may wear their "mess dress" or equivalent uniforms, which generally consist of the same elements but with appropriate insignia of the service and the rank of the wearer and miniature medals.
In proper use, a "tuxedo" is a black dinner jacket of a specific style that was first introduced several decades ago at an extablishment named The Tuxedo Club (
http://www.thetuxedoclub.org and click on the "Guest" button), from which it took its name, though many people improperly apply that term to any formal outfit.
As you correctly state, one should not substitute a dark business suit only unless the host (that is, the cruise line) indicates that such substitution is acceptable. Nonetheless, most cruise lines marketed in North America began allowing this substutition in the 1970's as a concession to the reality that most men who were likely to take cruises did not own formalwear but did own business suits. Alas, the advent of the "business casual" workplace has turned the tide so a lot fewer men now own business suits....
Norm.