'step by step' definitions:

Definition of 'step by step'

(from WordNet)
adverb
In a gradual manner; "the snake moved gradually toward its victim" [syn: gradually, bit by bit, step by step]
adverb
Proceeding in steps; "the voltage was increased stepwise" [syn: stepwise, step by step]

Synonyms of 'step by step'

From: Moby Thesaurus