What defines an entrepreneur? What qualities are considered the most important?

I'd say, first and foremost, grit. You're gonna (probably) fail multiple times, be short on money, and go through hard times.

Secondly, probably, the capacity to empathize, understand people, and get them to want to work for you. You want to have a strong team, people you can count on. Being able to read and judge people is important in that regard, as is having the open mind to understand them and care for them. Remember, being boss is not only having more power, it's also, and mainly, having more responsibilities (something most bosses forget).

Third, capacity to learn fast and react fast. You need to do google ads, but don't have the budget to hire a specialist? Then you'll have to become that specialist, and fast. Need to peruse some legal documents but your lawyer doesn't have time for you because you don't pay him/her enough? Better learn yourself some legalese. Etc.

Fourth, capacity to erase your ego. You had a great idea, and it didn't work, but it might be saved if it transformed into another idea? If your ego is too big to recognize it, or to accept other's suggestions and reward them for their contribution, you might still succeed, but you're much less likely to. Good entrepreneurs can think clearly and see ideas for their real worth, in isolation, whether the ideas come from them or from others, and don't cling to bad ideas blindly.

First Of all an entrepreneur is the one who is unique in everything , of course there are some qualities are important for that from My point of You  are as Follow :- 

1- Personal Feeling that you are entrepreneur.

2- Desire to be an entrepreneur.

3- Education& continuous Learning.

4- To Have Team work spirit 

5- work Experience.

6-Attitude & strong personality

7- Some natural skills such as (leadership- Good strategic  planing - listening- Job knowledge-