\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.

\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.