Bal·last n.
1. Naut. Any heavy substance, as stone, iron, etc., put into the hold to sink a vessel in the water to such a depth as to prevent capsizing.
2. Any heavy matter put into the car of a balloon to give it steadiness.
3. Gravel, broken stone, etc., laid in the bed of a railroad to make it firm and solid.
4. The larger solids, as broken stone or gravel, used in making concrete.
5. Fig.: That which gives, or helps to maintain, uprightness, steadiness, and security.
It [piety] is the right ballast of prosperity. --Barrow.
Ballast engine, a steam engine used in excavating and for digging and raising stones and gravel for ballast.
Ship in ballast, a ship carrying only ballast.