A gentleman is a man who does not cower to outside forces, he is strong and true to his word. He does the right thing, even if the right thing does not seem the popular thing. His strength of character is apparent in his presence as he enters a room and exerts not arrogance, but confidence that is contagious to others. A true gentleman never lacks a friend, because a true gentleman is a friend. The word 'Gentle' in gentleman is not in the sense that he is soft, but that with his confidence and aura, others might feel comfortable in his presence.
A man is a boy who has come of age; a gentleman is a man who left that boy behind.
A term of respect that in the modern age is often used and/or seen more in a derogatory way.
Don't call me sir, I work for a living!