The Collaborative International Dictionary of English v.0.48:

Genteel \Gen*teel"\, a. [F. gentil noble, pretty, graceful. See
   Gentle.]
   1. Possessing or exhibiting the qualities popularly regarded
      as belonging to high birth and breeding; free from
      vulgarity, or lowness of taste or behavior; adapted to a
      refined or cultivated taste; polite; well-bred; as,
      genteel company, manners, address.
      [1913 Webster]

   2. Graceful in mien or form; elegant in appearance, dress, or
      manner; as, the lady has a genteel person. Law.
      [1913 Webster]

   3. Suited to the position of lady or a gentleman; as, to live
      in a genteel allowance.

   Syn: Polite; well-bred; refined; polished.
        [1913 Webster]

WordNet (r) 3.0 (2006):

genteel
    adj 1: marked by refinement in taste and manners; "cultivated
           speech"; "cultured Bostonians"; "cultured tastes"; "a
           genteel old lady"; "polite society" [syn: civilized,
           civilised, cultivated, cultured, genteel,
           polite]

Moby Thesaurus II by Grady Ward, 1.0:

132 Moby Thesaurus words for "genteel":
   Victorian, affected, appropriate, aristocratic, artificial,
   becoming, blue-blooded, braw, cavalier, chic, chivalrous, civil,
   classy, clothes-conscious, confined, cosmopolitan, county,
   courteous, courtly, cultivated, cultured, dapper, dashing,
   debonair, decent, decorous, distingue, dressed to advantage,
   dressed to kill, ducal, elegant, exalted, exquisite, fashionable,
   felicitous, fitting, formal, gentle, gentlemanlike, gentlemanly,
   graceful, gracious, happy, high, high-class, highbred, insular,
   intolerant, jaunty, kinglike, kingly, knightly, la-di-da, ladylike,
   mannered, mannerly, meet, mincing, narrow, natty, neat, nifty,
   nobby, noble, of gentle blood, of rank, overdone, parochial,
   patrician, polished, polite, pompous, posh, pretentious, prig,
   priggish, princelike, princely, prissy, proper, provincial,
   prudish, puritanical, putting on airs, queenlike, queenly,
   quite the lady, recherche, refined, respectable, right, ritzy,
   royal, seemly, sharp, silk-stocking, sleek, smart, smug, snazzy,
   soigne, soignee, sophisticated, spiffy, spruce, stilted,
   straitlaced, stuffy, style-conscious, stylish, suave, suitable,
   swank, swanky, swell, thoroughbred, titled, tony, too-too, tricksy,
   trig, trim, uncharitable, unnatural, upper crust, urbane,
   well-behaved, well-bred, well-brought-up, well-dressed,
   well-groomed, well-mannered



The Devil's Dictionary (1881-1906):

GENTEEL, adj.  Refined, after the fashion of a gent.

    Observe with care, my son, the distinction I reveal:
    A gentleman is gentle and a gent genteel.
    Heed not the definitions your "Unabridged" presents,
    For dictionary makers are generally gents.
                                                                  G.J.