I. noun — [ mass noun] 1. heavy material, such as gravel, sand, or iron, placed in the bilge of a ship to ensure its stability. • the hull had insufficient ballast.
2. 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.
3. something providing stability or substance • the film is an entertaining comedy with some serious ideas thrown in for ballast.
4. 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.
5. a mixture of coarse and fine aggregate for making concrete. 6. [ count noun] — a passive component used in an electric circuit to moderate changes in current. • ballasts are permanently wired into existing fixtures.
• [as modifier]
II. verb — [with obj.] 1. give stability to (a ship) by putting a heavy substance in its bilge. • the vessel has been ballasted to give the necessary floating stability.
‹figurative› people insufficiently ballasted with factual information.
2. 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.
III. phrases in ballast (of a ship) laden only with ballast.
– origin mid 16th cent.: probably of Low German or Scandinavian origin.