a mixture of the diacid calcium salt of orthophosphoric acid Ca(H2PO4)2 with calcium sulphate and small quantities of other phosphates: used as a fertilizer
2.
a salt of phosphoric acid formed by incompletely replacing its acidic hydrogen atoms; acid phosphate; hydrogen phosphate
superphosphate in American English
(ˌsupərˈfɑsfeɪt)
noun
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