Gradually; little by little. An adverb indicating slow, step-by-step change or increase.
新しい仕事に少しずつ慣れてきた。
I've gradually gotten used to my new job.
貯金を少しずつ増やしている。
I'm slowly increasing my savings bit by bit.
問題は少しずつ解決していった。
The problems were solved little by little.
少しずつでいいから毎日勉強しなさい。
It's okay to do a little at a time, but study every day.