Superphosphate

noun

1. An acid phosphate.
2. A mixture of gypsum and monobasic calcium phosphate resulting from the action of sulfuric acid on phosphate rock, used as a fertilizer.
3. A trade-name of superphosphate of lime.
4. A phosphate containing the greatest amount of phosphoric acid that can combine with the base.
5. A trade-name for various phosphates, such as bone, bone-black, and phosphorite, which have been treated with sulphuric acid to increase their solubility, and so render them more available in agriculture as fertilizers.