Source : Webster's Revised Unabridged Dictionary (1913)

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.

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 : WordNet®

ballast
     v : make steady with a ballast

ballast
     n 1: any heavy material used to stabilize a ship or airship
     2: coarse gravel laid to form a bed for streets and railroads
     3: an attribute that tends to give stability in character and
        morals; something that steadies the mind or feelings
     4: a resistor inserted into a circuit to compensate for changes
        (as those arising from temperature fluctuations) [syn: {ballast
        resistor}, {barretter}]
     5: an electrical device for starting and regulating fluorescent
        and discharge lamps [syn: {light ballast}]