Ballast \Bal"last\, 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.

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.

Source: Webster's Revised Unabridged Dictionary (1913)
 

Ballast \Bal"last\, v. t. [imp. & p. p. Ballasted; p. pr. & vb. n. Ballasting.]

1. To steady, as a vessel, by putting heavy substances in the hold.

2. To fill in, as the bed of a railroad, with gravel, stone, etc., in order to make it firm and solid.

3. To keep steady; to steady, morally.

'T is charity must ballast the heart. --Hammond.

Source: Webster's Revised Unabridged Dictionary (1913)