a man of refinement
"The guest was welcomed as a gentleman because of his polite demeanor and impeccable manners."
a manservant who acts as a personal attendant to his employer
"Jeeves was Bertie Wooster's man"
A man of gentle but not noble birth, particularly a man of means (originally ownership of property) who does not work for a living but has no official status in a peerage; (Britain law) an armiferous man ranking below a knight.
"The newly wealthy merchant was addressed as "gentleman" at the club, despite his lack of noble title or knighthood."
In plain English: A gentleman is a man who acts with good manners and treats other people with respect.
"The gentleman helped me carry my heavy suitcase to the taxi."
Usage: Use this term to refer specifically to an upper-class man with wealth and refined manners rather than any ordinary male. Avoid using it as a generic polite address unless you are in the UK or addressing someone known to belong to that social class.
A surname, from nicknames.
"The family tree traces their lineage back to a distant ancestor whose nickname became the surname Gentleman."
The word entered English from the phrase gentilhomme in Old French, combining the idea of being noble or well-born with "man." It originally referred to a person of high birth and good manners rather than simply any male adult.