The Collaborative International Dictionary of English v.0.48:

Fastidious \Fas*tid"i*ous\, a. [L. fastidiosus disdainful, fr.
   fastidium loathing, aversion, perh. fr. fastus arrogance (of
   uncertain origin) + taedium loathing. Cf. Tedious, Fash.]
   Difficult to please; delicate to a fault; suited with
   difficulty; squeamish; as, a fastidious mind or ear; a
   fastidious appetite.
   [1913 Webster]

         Proud youth ! fastidious of the lower world. --Young.

   Syn: Squeamish; critical; overnice; difficult; punctilious.


   Usage: Fastidious, Squeamish. We call a person fastidious
          when his taste or feelings are offended by trifling
          defects or errors; we call him squeamish when he is
          excessively nice or critical on minor points, and also
          when he is overscrupulous as to questions of duty.
          "Whoever examines his own imperfections will cease to
          be fastidious; whoever restrains his caprice and
          scrupulosity will cease to be squeamish." --Crabb. --
          Fas*tid"i*ous*ly, adv. -- Fas*tid"i*ous*ness, n.
          Fastigiate

WordNet (r) 3.0 (2006):

fastidiously
    adv 1: in a fastidious and painstaking manner; "it is almost a
           waste of time painstakingly to learn the routines of
           selling" [syn: painstakingly, fastidiously]
    2: in a fastidious manner; "he writes extremely musical music,
       of which the sound is fastidiously calculated and yet
       agreeably spontaneous and imaginative"