How do you define entrepreneurship?

I'll build off what @falcon00 said — I think all too often entrepreneurship is shined on solely starting your own company, whereas there as so many talented entrepreneurs that operate within bigger corporate environments, and build incredible ventures to create new revenue streams, partnerships, etc. You don't have to be the founder of a company, but rather if you have the know-how and skill set to build something brand new and innovate within an existing company, I consider that person to be a talented entrepreneur.

Make shit. Sell shit.

It's not a definition but a funny joke. I mean, as entrepreneurs, we have to keep calm and work smart (or not, which is also fine, we call it experience). Anyway, here's the joke :))

A young businessman had just started his own firm. He rented a beautiful office and had it furnished with antiques. Sitting there, he saw a man come into the outer office.

Wishing to appear the hot shot, the businessman picked up the phone and started to pretend he had a big deal working.

He threw huge figures around and made giant commitments. Finally he hung up and asked the visitor, “Can I help you?”

The man said, “Yeah, I’ve come to activate your phone lines.”

Entrepreneurs are people who find the missing piece of the puzzle.
It is hard to see for a lot of people. It is not about only finding ideas. Entrepreneurs are best puzzle solvers for sales, team management and operating their bussiness.

I would define entrepreneurship as starting any new business, regardless of whether or not it's a startup.

I would define a startup as a business that's been founded specifically to arbitrage a temporary economic disequilibrium in order to achieve otherwise impossible rates of growth.