poz·zo·lan 
(pŏt′sə-län) also poz·zo·la·na (-sə-länə) or poz·zuo·la·na (-swə-)
(pŏt′sə-län) also poz·zo·la·na (-sə-länə) or poz·zuo·la·na (-swə-)n.
1. A siliceous volcanic ash used to produce hydraulic cement.
2. Any of various powdered substances that react with lime to form strengthening or enhancing compounds in cement.
[Italian pozzolana, after Pozzuoli.]
poz′zo·lanic adj.