Although the Neolithic Revoltions took like ages (thousand of years before it spread across the Old World), the way it transformed the way of life for humans was so intense historians refer it to as a revolution. The change from hunter-gatherers to sedentary farmers had an deep impact to human society and changed our story forever.

Creds: I'm a history student at the University of Amsterdam

One of the meanings of the word revolution is

a sudden, complete or marked change in something (definition 3 at Dictionary.com)

Another example of this usage is the Industrial Revolution.

What we think of when we think of revolutions are political revolutions, such as the American Revolution or the French Revolution, but the term has a broader meaning than that, and describes a sweeping, fundamental change to the way things are.

The Neolithic Revolution is perhaps the most fundamental of these complete, marked changes. It consists basically of the change from the hunter-gatherer mode of subsistence to semi-sedentary agricultural mode of subsistence. Basically, during the Neolithic Revolution, people discovered how to farm. They discovered how to cause useful plants to grow, and how to domesticate animals as well.

Why was this so important? The short answer is, it directly led to urbanization, craft specialization, and what we think of as civilization.

The rise of agriculture meant that people could create surpluses of food. It also meant that because there was a surplus of food, other people could come and take that surplus of food. It also meant that people had to settle down and live in one place for a much longer time (pastoralists, or animal herders, would have a couple places they would cycle between, to ensure fresh pastures for their animals). This meant that people began to live together in settlements, for protection from raiders among other reasons. Because agriculture allows fewer people to feed more people, it allowed for craft specialization, people whose time was no longer devoted to obtaining food, because the farmers took care of that for them. So these people could devote their time to creating art objects, developing metalworking and innovating new tools, developing governments and religious institutions to organize these groups of people living together, and trading these new goods with other settlements doing the same thing.

I would argue that there are very few major changes (revolutions) that have as much of a fundamental impact on humanity.