The Collaborative International Dictionary of English v.0.48:

Fashionable \Fash"ion*a*ble\, a.
   1. Conforming to the fashion or established mode; according
      with the prevailing form or style; as, a fashionable
      dress.
      [1913 Webster]

   2. Established or favored by custom or use; current;
      prevailing at a particular time; as, the fashionable
      philosophy; fashionable opinions.
      [1913 Webster]

   3. Observant of the fashion or customary mode; dressing or
      behaving according to the prevailing fashion; as, a
      fashionable man.
      [1913 Webster]

   4. Genteel; well-bred; as, fashionable society.
      [1913 Webster]

            Time is like a fashionable host
            That slightly shakes his parting guest by the hand.
                                                  --Shak.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Fashionable \Fash"ion*a*ble\, n.
   A person who conforms to the fashions; -- used chiefly in the
   plural.
   [1913 Webster]

WordNet (r) 3.0 (2006):

fashionable
    adj 1: being or in accordance with current social fashions;
           "fashionable clothing"; "the fashionable side of town";
           "a fashionable cafe" [syn: fashionable, stylish]
           [ant: unfashionable, unstylish]
    2: having elegance or taste or refinement in manners or dress;
       "a little less posh but every bit as stylish as Lord Peter
       Wimsey"; "the stylish resort of Gstadd" [syn: stylish,
       fashionable] [ant: styleless, unstylish]
    3: patronized by

Moby Thesaurus II by Grady Ward, 1.0:

65 Moby Thesaurus words for "fashionable":
   Beau Brummel, a la mode, advanced, all the rage, all the thing,
   arbiter of fashion, avant-garde, chic, clotheshorse, clubman,
   clubwoman, contemporary, current, dandy, dashing, deb, debutante,
   exclusive, far out, fashion plate, fop, forward-looking, hip, in,
   in fashion, in style, in vogue, man-about-town, mod, modern,
   modernistic, modernized, modish, mondain, mondaine, new,
   newfashioned, now, popular, present-day, present-time, prevalent,
   progressive, smart, socialite, streamlined, stylish, subdeb,
   subdebutante, swank, swinger, swish, taste-maker, tone-setter,
   trend-setter, trendy, twentieth-century, ultra-ultra, ultramodern,
   up-to-date, up-to-datish, up-to-the-minute, way out, with it,
   with-it