ballast
noun
[ ˈbaləst ]
• heavy material, such as gravel, sand, or iron, placed in the bilge of a ship to ensure its stability.
• "the hull had insufficient ballast"
• gravel or coarse stone used to form the bed of a railway track or the substratum of a road.
• "a thick layer of railway ballast"
• a passive component used in an electric circuit to moderate changes in current.
• "ballasts are permanently wired into existing fixtures"
ballast
verb
• give stability to (a ship) by putting a heavy substance in its bilge.
• "the vessel has been ballasted to give the necessary floating stability"
• form (the bed of a railway line or the substratum of a road) with gravel or coarse stone.
• "the track was laid with rails and ballasted with earth"
Origin:
mid 16th century: probably of Low German or Scandinavian origin.
in ballast
• (of a ship) laden only with ballast.