The Collaborative International Dictionary of English v.0.48:

Beautiful \Beau"ti*ful\ (b[=u]"t[i^]*f[.u]l), a.
   Having the qualities which constitute beauty; pleasing to the
   sight or the mind.
   [1913 Webster]

         A circle is more beautiful than a square; a square is
         more beautiful than a parallelogram.     --Lord Kames.
   [1913 Webster]

   Syn: Handsome; elegant; lovely; fair; charming; graceful;
        pretty; delightful. See Fine. -- Beau"ti*ful*ly,
        adv. -- Beau"ti*ful*ness, n.
        [1913 Webster]

WordNet (r) 3.0 (2006):

beautiful
    adj 1: delighting the senses or exciting intellectual or
           emotional admiration; "a beautiful child"; "beautiful
           country"; "a beautiful painting"; "a beautiful theory";
           "a beautiful party" [ant: ugly]
    2: (of weather) highly enjoyable; "what a beautiful day"