an acid phosphate, esp. a mixture mainly of monobasic calcium phosphate and gypsum, made by treating bone, phosphate rock, etc. with sulfuric acid and used as fertilizer
See superphosphate in American Heritage Dictionary 4
noun
An acid phosphate.
A mixture of gypsum and monobasic calcium phosphate resulting from the action of sulfuric acid on phosphate rock, used as a fertilizer.