Pronunciation: (ri-tär'dur), [key]
1. a person or thing that retards.
a. any substance added to rubber to delay or prevent vulcanization.
b. any substance added to delay a process.
3. Building Trades.an admixture of concrete or plaster that retards its set.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.