This word is acceptable for play in the US & UK dictionaries that are being used in the following games:

• Lexulous
• Wordscraper
• Wordosaur

adj. Marked by a gradual progression as if step by step: "Quantum mechanics is a natural system of stepwise interactions that governs very small things” ( Malcom W. Browne).

adj. Music Moving from one tone to an adjacent one.

adj. One (small) step or stage at a time; gradual; piecemeal

ad. One step or stage at a time; step by step

ad. proceeding in steps

adj. one thing at a time

"When Mosher and Pratt broke out the figures by age, the percentage of those expected to suffer from impaired fecundity increased in stepwise fashion."

gradual   

second-pass    step-wise    particle-acceleration    picometer    wavelike