The Collaborative International Dictionary of English v.0.48:

Greatly \Great"ly\, adv.
   1. In a great degree; much.
      [1913 Webster]

            I will greatly multiply thy sorrow.   --Gen. iii.
                                                  16.
      [1913 Webster]

   2. Nobly; illustriously; magnanimously.
      [1913 Webster]

            By a high fate thou greatly didst expire. --Dryden.
      [1913 Webster]

WordNet (r) 3.0 (2006):

greatly
    adv 1: to an extraordinary extent or degree; "he improved
           greatly"

Moby Thesaurus II by Grady Ward, 1.0:

48 Moby Thesaurus words for "greatly":
   a deal, a great deal, a lot, abundantly, as all creation,
   as all get-out, beaucoup, consequentially, considerable,
   considerably, conspicuously, eminently, ever so, ever so much,
   exceedingly, exceptionally, extremely, galore, grandly, highly,
   hugely, importantly, in great measure, largely, markedly,
   materially, momentously, much, muchly, never so, no end, no end of,
   not a little, notably, outstandingly, plenty, pretty much,
   prominently, remarkably, saliently, signally, significantly, so,
   so very much, strikingly, surpassingly, to the skies, very much