1heavy material, such as gravel, sand, or iron, placed in the bilge of a ship to ensure its stability:the hull had insufficient ballast
a heavy substance carried in an airship or on a hot-air balloon to stabilize it and jettisoned when greater altitude is required:a forty kilo sandbag was used as ballast
something providing stability or substance:the film is an entertaining comedy with some serious ideas thrown in for ballast
2gravel 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 mixture of coarse and fine aggregate for making concrete.
3 [count noun] a passive component used in an electric circuit to moderate changes in current:ballasts are permanently wired into existing fixtures [as modifier]:ballast resistors
1give stability to (a ship) by putting a heavy substance in its bilge:the vessel has been ballasted to give the necessary floating stability figurativepeople insufficiently ballasted with factual information
2form (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
(of a ship) laden only with ballast.
mid 16th century: probably of Low German or Scandinavian origin
ballast in other Oxford dictionaries
Definition of ballast in the US English dictionary