The Collaborative International Dictionary of English v.0.48:

Fundamentally \Fun`da*men"tal*ly\, adv.
   Primarily; originally; essentially; radically; at the
   foundation; in origin or constituents. "Fundamentally
   defective." --Burke.
   [1913 Webster]

WordNet (r) 3.0 (2006):

fundamentally
    adv 1: in essence; at bottom or by one's (or its) very nature;
           "He is basically dishonest"; "the argument was
           essentially a technical one"; "for all his bluster he is
           in essence a shy person" [syn: basically,
           fundamentally, essentially]

Moby Thesaurus II by Grady Ward, 1.0:

40 Moby Thesaurus words for "fundamentally":
   a outrance, absolutely, all out, at bottom, at heart, at the core,
   au fond, basically, beyond all bounds, beyond compare,
   beyond comparison, beyond measure, completely, dead, downright,
   essentially, extremely, flat out, immeasurably, in essence,
   in itself, in substance, in the extreme, in the main, incalculably,
   indefinitely, infinitely, materially, most, per se, perfectly,
   primarily, purely, radically, substantially, totally,
   unconditionally, unequivocally, utterly, with a vengeance