stepping-stone
nounUK /ˈstepɪŋ stəʊn/
US /ˈstepɪŋ stoʊn/
A stepping-stone is a flat stone you step on to cross water or mud.
We used stepping-stones to cross the little stream without getting wet.
OTHER MEANINGS
2. Something that helps you reach a goal or move forward.
Her first job was a stepping-stone to a career in science.
3. A flat stone set in the ground to walk on.
The garden path was made of round stepping-stones.
4. A person or thing used by someone to get ahead.
He treated his old friends as stepping-stones to success.