Cleo you surprise me, is this perhaps a US term as it isa very common one there.
I would describe it as like a spider web of light brown scarring on the fruits skin, particularly more so on the shoulders ,some varieties are more resistant than others,can be caused by stress to the plant during blossom time, excess ammonia in fertiliser can do it, but it is usually very high or very low temeratures.
Nyagous by the way is one of my favourite tomatoes, it is a very smooth lovely looking tom with a superb taste. XX Jeannine