A dense thicket of pubic hair (in this case referring to a woman, but the term is genderless) that seems almost impenetrable. This coarse bush often extends down on either sides of the vagina and partially obscures it.
A pubic bramble causes one to recoil in awkward disgust and immediately lose interest in what was presumably an acceptable female.
A pubic bramble may also be said to have the roughness of a frayed burlap sack.
Pssst, look over there, thats the girl with the pubic bramble.