From WordNet (r) 3.0 (2006) [wn]:
gradually
adv 1: in a gradual manner; "the snake moved gradually toward
its victim" [syn: gradually, bit by bit, {step by
step}]
From The Collaborative International Dictionary of English v.0.48 [gcide]:
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]