Pronunciation: (bī-tOO'mun, -tyOO'-, bi-, bich'oo-), [key]
1. any of various natural substances, as asphalt, maltha, or gilsonite, consisting mainly of hydrocarbons.
2. (formerly) an asphalt of Asia Minor used as cement and mortar.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.