ballast

n. [ D. ballast; akin to Dan. baglast, ballast, OSw. barlast, Sw. ballast. The first part is perh. the same word as E. bare, adj.; the second is last a burden, and hence the meaning a bare, or mere, load. See Bare, a., and Last load. ] 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. [ 1913 Webster ]

2. Any heavy matter put into the car of a balloon to give it steadiness. [ 1913 Webster ]

3. Gravel, broken stone, etc., laid in the bed of a railroad to make it firm and solid. [ 1913 Webster ]

4. The larger solids, as broken stone or gravel, used in making concrete. [ 1913 Webster ]

5. Fig.: That which gives, or helps to maintain, uprightness, steadiness, and security. [ 1913 Webster ]

It [ piety ] is the right ballast of prosperity. Barrow. [ 1913 Webster ]

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. [ 1913 Webster ]