Pronunciation: (mal'thu), [key]
1. a liquid bitumen used in ancient times as a mortar or waterproofing agent.
2. any of various natural mixtures of bituminous hydrocarbons.
3. a viscous mineral liquid or semiliquid bitumen; a mineral tar.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.