A couple of people have posted the widely used definition.
If the firearm routinely shoots small groups, it is precise. Precision is getting the same result every time you apply the same stimulus.
A firearm is accurate if the long term average of many shots is at the intended target. A well sighted-in SKS might be very accurate, but probably not very precise.
Lack of precision is harder to fix. But if you're trying for a firearm that will help you win a competition, precision is where you have to start: good barrel, proper bedding, consistent ammunition, solid bench rest, etc., and above all, excellent shooting skill.
Once precision is attained, then getting accuracy is easy: crank the elevation and windage on the scope.