Is it blackberry bushes?
Read Brer Rabbit, and then you'll know!
Bushes is a little bit optomistic... it is the tangled mess you get when an unteded Bramble (Blackberry) is left to tip root in all directions and self sown ones grow up from the birds eating the fruit.... the patch is usually shoulder high (I'm 6') and covers about 1/2 the plot...
I've cleared a few like that on this site...
:o
cheers!