The Collaborative International Dictionary of English v.0.48:

Utterly \Ut"ter*ly\, adv.
   In an utter manner; to the full extent; fully; totally; as,
   utterly ruined; it is utterly vain.
   [1913 Webster]

WordNet (r) 3.0 (2006):

utterly
    adv 1: completely and without qualification; used informally as
           intensifiers; "an absolutely magnificent painting"; "a
           perfectly idiotic idea"; "you're perfectly right";
           "utterly miserable"; "you can be dead sure of my
           innocence"; "was dead tired"; "dead right" [syn:
           absolutely, perfectly, utterly, dead]

Moby Thesaurus II by Grady Ward, 1.0:

50 Moby Thesaurus words for "utterly":
   a outrance, a toute outrance, absolutely, all hollow, all out,
   all the way, altogether, beyond all bounds, beyond compare,
   beyond comparison, beyond measure, categorically, completely, dead,
   definitely, downright, entirely, essentially, extremely, flat out,
   fully, fundamentally, head over heels, immeasurably,
   in the extreme, incalculably, indefinitely, infinitely, most,
   out-and-out, perfectly, proper, properly, purely, radically,
   thoroughly, to a fare-you-well, to the backbone, to the full,
   to the limit, to the marrow, to the skies, to the sky,
   to the utmost, totally, unconditionally, unequivocally,
   unreservedly, wholly, with a vengeance