My friend just moved into a new house, and found this growing by her back door. It has some wicked thorns, both on the stem and at the terminus of the leaves. Her husband weed-whacked it when it first showed up and now it's grown back bigger and thicker. Also, it seems angry.
Does any one recognize it? Their kids have been calling it Audrey III.
She emailed me the photo - hope someone can tell what it is with this sort of funky angle (I think she was trying to show the thorn on the end of the leaf.)