The Collaborative International Dictionary of English v.0.48:

AEsthetic \[AE]s*thet"ic\, AEsthetical \[AE]s*thet"ic*al\, a.
   Of or Pertaining to [ae]sthetics; versed in [ae]sthetics; as,
   [ae]sthetic studies, emotions, ideas, persons, etc.
   [1913 Webster] -- [AE]s*thet"ic*al*ly, adv.
   [1913 Webster]

WordNet (r) 3.0 (2006):

aesthetic
    adj 1: relating to or dealing with the subject of aesthetics;
           "aesthetic values" [syn: aesthetic, esthetic]
    2: concerning or characterized by an appreciation of beauty or
       good taste; "the aesthetic faculties"; "an aesthetic person";
       "aesthetic feeling"; "the illustrations made the book an
       aesthetic success" [syn: aesthetic, esthetic,
       aesthetical, esthetical] [ant: inaesthetic,
       unaesthetic]
    3: aesthetically pleasing; "an artistic flower arrangement"
       [syn: aesthetic, esthetic, artistic]
    n 1: (philosophy) a philosophical theory as to what is
         beautiful; "he despised the esthetic of minimalism" [syn:
         aesthetic, esthetic]

Moby Thesaurus II by Grady Ward, 1.0:

46 Moby Thesaurus words for "aesthetic":
   Attic, aesthetically appealing, art-conscious, artistic, arty,
   attractive, beauteous, beautiful, chaste, choice, classic,
   cultivated, discriminating, elegant, endowed with beauty,
   excellent, exquisite, eye-filling, fine, flowerlike, graceful,
   gracile, handsome, heavy, in good taste, lovely, of choice,
   of consummate art, of quality, ornamental, painterly, pleasing,
   pretty, pulchritudinous, pure, quiet, refined, restrained,
   sensitive, simple, subdued, tasteful, unaffected, understated,
   unobtrusive, well-chosen