Just food for thought, here's Robert E. Lee's definition of a gentleman:
The forbearing use of power does not only form a touchstone, but the manner in which an individual enjoys certain advantages over others is a test of a true gentleman.
The power which the strong have over the weak, the employer over the employed, the educated over the unlettered, the experienced over the confiding, even the clever over the silly — the forbearing or inoffensive use of all this power or authority, or a total abstinence from it when the case admits it, will show the gentleman in a plain light.
The gentleman does not needlessly and unnecessarily remind an offender of a wrong he may have committed against him. He can not only forgive, he can forget; and he strives for that nobleness of self and mildness of character which impart sufficient strength to let the past be but the past. A true man of honor feels humbled himself when he cannot help humbling others.
Lee's definition is the closest I've found to what I was taught, which is a gentleman is honest, polite, trustworthy, and respectful. A man whose word is his bond. A man of integrity and honor.
Good manners is just a natural side effect of the character of a gentleman. I guess what struck me the wrong way with the wikipedia article on gentleman (
http://en.wikipedia.org/wiki/Gentleman) was the trivialization of a gentleman to just a person with good manners.