bal·last /ˈbæləst/
 壓艙物,壓載,沙袋;鎮流器;鎮定,沈著
 Bal·last n.
 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 carrying 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.
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 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]
      v : make steady with a ballast