Source : Webster's Revised Unabridged Dictionary (1913)

Greatly \Great"ly\, adv.
   1. In a great degree; much.

            I will greatly multiply thy sorrow.   --Gen. iii.
                                                  16.

   2. Nobly; illustriously; magnanimously.

            By a high fate thou greatly didst expire. --Dryden.

Source : WordNet®

greatly
     adv : to a great extent or degree; "he improved greatly"; "greatly
           reduced"