The Collaborative International Dictionary of English v.0.48:

Gentleman \Gen"tle*man\, n.; pl. Gentlemen. [OE. gentilman
   nobleman; gentil noble + man man; cf. F. gentilhomme.]
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   1. A man well born; one of good family; one above the
      condition of a yeoman.
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   2. One of gentle or refined manners; a well-bred man.
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   3. (Her.) One who bears arms, but has no title.
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   4. The servant of a man of rank.
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            The count's gentleman, one Cesario.   --Shak.
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   5. A man, irrespective of condition; -- used esp. in the
      plural (= citizens; people), in addressing men in popular
      assemblies, etc.
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   Note: In Great Britain, the term gentleman is applied in a
         limited sense to those having coats of arms, but who
         are without a title, and, in this sense, gentlemen hold
         a middle rank between the nobility and yeomanry. In a
         more extended sense, it includes every man above the
         rank of yeoman, comprehending the nobility. In the
         United States, the term is applied to men of education
         and good breeding of every occupation.
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   Gentleman commoner, one of the highest class of commoners
      at the University of Oxford.

   Gentleman usher, one who ushers visitors into the presence
      of a sovereign, etc.

   Gentleman usher of the black rod, an usher belonging to the
      Order of the Garter, whose chief duty is to serve as
      official messenger of the House of Lords.

   Gentlemen-at-arms, a band of forty gentlemen who attend the
      sovereign on state occasions; formerly called gentlemen
      pensioners. [Eng.]
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