1. the favorable or prosperous termination of attempts or endeavors.
2. the attainment of wealth, position, honors, or the like.
3. a successful performance or achievement: The play was an instant success.
Pulled from Dictionary.com
I like the first definition, it allows more flexibility. Favorable termination could mean a lot of things. When people think of a start-up company there are usually three possible outcomes - 1.The company grows quickly and gains revenues/profits and everyone is happy 2. company fails quickly and although you may not be rich, you were happy to learn from this experience 3. company just meanders along without growing or dieing and no one is happy. I would consider the first two outcomes a success. But if you use the 2nd definition of success (posted above) only growing quickly and attaining profits is a success.
The second definition of success discounts any action that does not result in wealth or honors. I think this definition of success leads people to appreciate their actions less than they should. I spent an afternoon with my son just walking around the block and talking about the city around us. It was my favorite part of my day, and yet I did not achieve success in something measurable like wealth or position. If I use the first definition for success, I would say it was very favorable termination to that part of my day. Always remember that there are multiple definitions of success.