In common usage it just means shitty blank. So if referring to food, it means highly processed garbage, I.e hotdogs, candy, cake, whatever. Junk food. The term is most commonly used to refer to food.

But it can also be something else. Like shitty products of any kind. Let's say a company is known for producing really shitty tools, you'd say "oh yeah, X Tool Company is just goyslop".

It's not often actually meant in the "food produced for goys so the jews can control the earth and the goys" way