What is the Militia?

From the JPFO:

One of the most common arguments gun-prohibitionists use is that the term "militia" in the Second Amendment refers to States' right to maintain an army -- that is, the National Guard.

We all know better, and here's proof. Following is a scan from the 1771 edition of the Encyclopedia Britannica. You can see a scan of the whole page, plus the cover page, in PDF format here.

The definition of militia reads:

MILITIA, in general, denotes the body of soldiers, or those who make profession of arms.
.....In a more restrained sense, militia denotes the trained bands of a town or country, who arm themselves, upon a short warning, for their own defence. So that, in this sense, militia is opposed to regular or stated troops.
.....For the direction and command of the militia, the king constitutes lords-lieutenants of each country.