help!!! slack tipper definition

You probably mean slag tipper. That was a real occupation. FYI, fine granular pieces of coal was called slack in some parts of England.

Dr. Mike napisal(a):

But what exactly does a slag tipper do?! Is it a person who loads coal in a steelworks coking plant? M.M.

The slag (waste) is poured off from the molten metal at intervals then dumped to get rid of it. Locally, it was driven on a rail track in side tipping containers up a hill. At the top, the partially solidified slag was tipped out. At the bottom of the hill, the cold slag was ground up, mixed with asphalt then spread on the roads as tarmac. So it is not a total waste.