basic slag

from the GNU version of the Collaborative International Dictionary of English.

• A by-product from the manufacture of steel by the basic process, used as a fertilizer. It is rich in lime and contains 14 to 20 per cent of phosphoric acid. Called also Thomas slag, phosphatic slag, and odorless phosphate.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun slag produced in making steel; low in silica but having large amounts of calcium phosphate; useful as fertilizer