are the leaves kind of spotted? I don't know what it is, but I get it also. I just dig it out. Grabbed ahold of one today by accident, man they hurt!

It sounds like one of the species of Greenbrier (Smilax sp.).

Look at the images linked below and see if any of them resemble it.

We have several kinds of them growing wild here in our woods, and occasionally the come up in the garden.

It is hard to dig up because the roots are very large and can run very deeply.

You can kill it by pruning it back hard, waiting until a couple of new leaves sprout, and then painting a chemical stump killer onto the new growth. You may have to reapply several times.

The first few years after we moved here, we spent every winter removing this stuff from our woods. It had been growing wild there for decades and the vines at the ground were almost as big around as my wrist and were more like trees than vines. We used the chain saw to cut through them.

Dawn

Here is a link that might be useful: Assorted Images of Greenbrier