ballast

ballast is a Noun

Definition:

[1] 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 carring only ballast.