The Collaborative International Dictionary
Pozzuolana
Pozzuolana \Poz`zu*o*la"na\, Pozzolana \Poz`zo*la"*na\, n. [It.] Volcanic ashes from Pozzuoli, in Italy, used in the manufacture of a kind of mortar which hardens under water.
Wiktionary
pozzuolana
n. (alternative spelling of pozzolana English)