The Collaborative International Dictionary of English v.0.48:

Unusual \Un*u"su*al\, a.
   Not usual; uncommon; rare; as, an unusual season; a person of
   unusual grace or erudition. -- Un*u"su*al*ly, adv. --
   Un*u"su*al*ness, n.
   [1913 Webster]

WordNet (r) 3.0 (2006):

unusually
    adv 1: to a remarkable degree or extent; "she was unusually
           tall" [syn: unusually, remarkably, outstandingly,
           unco] [ant: commonly, normally, ordinarily,
           unremarkably, usually]

Moby Thesaurus II by Grady Ward, 1.0:

57 Moby Thesaurus words for "unusually":
   abnormally, abundantly, acutely, amazingly, amply, astonishingly,
   awesomely, conspicuously, copiously, eminently, emphatically,
   exceptionally, exquisitely, extraordinarily, exuberantly, famously,
   generously, glaringly, hardly, hardly ever, impressively,
   incredibly, intensely, magically, magnanimously, magnificently,
   markedly, marvelously, nobly, notably, particularly, peculiarly,
   pointedly, preeminently, profusely, prominently, pronouncedly,
   rarely, remarkably, richly, seldom, seldom if ever, signally,
   singularly, splendidly, strikingly, superlatively, surpassingly,
   surprisingly, uncommonly, uncustomarily, unexpectedly, unnaturally,
   unordinarily, wonderfully, wondrous, worthily