Self-defined, of course. Your parents usually just want you to be happy and self-sufficient: able to support yourselves living a middle-class lifestyle, usually. Depending on the parent or teacher or other adult, they may have additional visions: maybe of you rising above (or matching, if you grew up wealthy) their own socioeconomic status and becoming wealthy, or of you becoming powerful in a political sense, or well-traveled or working in a prestigious position. Some parents and teachers have specific expectations: they want you to be a doctor, a lawyer, an engineer, something else.
My definition was working in a position I enjoyed and making enough money to support myself and my lifestyle.