The word "entrepreneur" is French and literally means "one who undertakes a task." It has come to mean, in English, "a person who organizes and manages any enterprise, especially a business, usually with considerable initiative and risk" (Dictionary.com).
You will note the definition says "especially a business," but not exclusively a business. So, buying and selling, while it is definitely part of most entrepreneurship, doesn't define it. For example, billionaire Richard Branson, of the multiple Virgin entities, could absolutely be held up as an icon of entrepreneurship: He started Virgin Records while a penniless teenager and keeps spinning off what many would regard as "risky" businesses even today.
But someone like Bill McKibben of 350.org could also be regarded as an entrepreneur, having built a powerful environmental nonprofit from scratch.
"Initiative" and "risk" are keys words in the definition. Entrepreneurship involves valuing your own ideas and your own ability to transform them into reality, and it also involves being willing, even eager, to take risks. Being an entrepreneur is not for the faint of heart, those who are afraid to fail, nor those who need micromanagement.