1) A heavy material used to provide weight and/or stability. Ballast is commonly used in hot-air balloons, ships, and submarines. Examples of materials used for ballast include water, sand, and iron.
2) Crushed concrete, slag, or stone used as a foundation for railroad beds.
Sources Checked for Data in Record
- Random House, Webster's Encyclopedic Unabridged Dictionary of the English Language, Grammercy Book, New York, 1997
- The American Heritage Dictionary or Encarta, via Microsoft Bookshelf 98, Microsoft Corp., 1998