ambitious adjective. › having a ​strong ​desire for ​success, ​achievement, ​power, or ​wealth: Even as a ​young man he was ambitious and ​self-assured. › If you ​describe an ​activity as ambitious, you ​mean that it ​involves a lot of ​effort or ​expense: It was an ambitious ​project to ​restore the ​public ​parks.