The Collaborative International Dictionary of English v.0.48:

Gradually \Grad"u*al*ly\, adv.
   1. In a gradual manner.
      [1913 Webster]

   2. In degree. [Obs.]
      [1913 Webster]

            Human reason doth not only gradually, but
            specifically, differ from the fantastic reason of
            brutes.                               --Grew.
      [1913 Webster]

WordNet (r) 3.0 (2006):

gradually
    adv 1: in a gradual manner; "the snake moved gradually toward
           its victim" [syn: gradually, bit by bit, step by
           step]