What do you think people mean when they say their "weapon is an extension of their arm?

Practicing with a weapon until you can feel as though your weapon is an extension of your body. Old school bow staff masters used to require their student carry their staff all day whatever they were doing. In fact the hand held weapon is an extension of your body. Even a hand gun, or long gun, or rifle is an extension of your body. Being comfortable in handling it and familiar with it's feel so that moving it is a natural thing, a reflexive thing.

It means you have the right to cut off the arms of a grizzly bear and replace your own arms with those! It's in the Bill of Rights and it is a hotly debated subject. It's about guns and that's as far as I'm going. If you want more information visit the websites of the NRA and Brady Campaign. They are two opposing interest groups. They will give you a lot of different information about the Second Amendment. You can form your own opinion from there after that.

It means you need skill to handle a weapon properly, and that a weapon is no substitute for poor combat skills. Your arms can be very dangerous if trained right, and a weapon can make them even more so, but the average person can be easily disarmed by someone with the right training. In essence your weapon is only as useful as your arm is.

It means exactly that.

Only, it generally applies to hand-held weapons - not trajectory ones, like bows, guns, and the like.

The idea is that the arms and hands move as if there were no weapon held.

Some people get the idea that it has something to do with moving the weapon. You don't move the weapon - you move your arms and hands.

When people say that, they mean that they are both comfortable and skillful enough with the weapon to use it any way they wish without having to even think about it, without even having to look at the weapon.

Want to scratch the itch on your nose? Just use the tip of the sword to scratch your nose without even looking at the sword. That's what people mean by that phrase.

I see it as its the same principles applied to the weapon as your body.

In old fencing everything was the same the sword, spear & quarterstaff were all used exactly the same albeit slightly different uses because of surface areas like a quarterstaff compared to a spear produce different results.

even boxing was fencing with the fists which goes with the idea of everything's the same in principles & concepts but differ only slightly in application.

here's an example of boxing being fencing with the fists- http://i.imgur.com/dga1e.png

You have to use that weapon as if it's a part of your own body.

its exactly as stated, its an extension part of your body, where you move the weapon moves. if you dont treat it as part of your body your not using it correctly

to me, it means that the weapon is (supposed to be) used like it's your own limb, that is, with perfect control over what it can do and what you want it to do.