Learner's definition of AMBITIOUS
[more ambitious; most ambitious]
having a desire to be successful, powerful, or famous
The company was created by two very ambitious young men in the early 1900s.
He was very ambitious for his children but not for himself. [=he wanted his children to be successful but he didn't feel the need to be successful himself]
not easily done or achieved
requiring or showing ambition
This 500-page book is her most ambitious effort/project yet.
Your plans for the future are very ambitious.
It was too ambitious a task for just one person.