Definition of "slagheap"

The smoke-pall of industrial Lancashire hung over the landscape; perhaps slagscape would be a more fitting term. The general prospect was a succession of chimney-stacks, factories, pit-heads, slagheaps, junctions, sidings and coal wagons.

1949 January and February, F. G. Roe, “I Saw Three Englands–1”, in Railway Magazine, page 11