\Su`per*phos"phate\, n. (Chem.)
An acid phosphate.
{Superphosphate of lime} (Com. Chem.), a fertilizer obtained
   by trating bone dust, bone black, or phosphorite with
   sulphuric acid, whereby the insoluble neutral calcium
   phosphate, {Ca3(PO4)2}, is changed to the primary or acid
   calcium phosphate {Ca(H2PO4)2}, which is soluble and
   therefore available for the soil.