it means it has had all the crap removed from it. However topsoil is a very loose term. there are different grades and different definitions of screening. e went to a job where one couple had paid £120 for a load of topsoil to be put in their front garden. Very nicely screened, except it was pure clay that had been put there. Sample it first and if you dont like the look of it dont accept it. get it from a decent landscape supplier, you get what you pay for