ballast

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. Heavy material that is placed in the hold of a ship or the gondola of a balloon to enhance stability.
2. n. Coarse gravel or crushed rock laid to form a bed for roads or railroads.
3. n. The gravel ingredient of concrete.
4. n. Something that gives stability, especially in character.
5. v. To stabilize or provide with ballast.
6. v. To fill (a railroad bed) with or as if with ballast.

Century Dictionary and Cyclopedia

1. n. Weight carried by a ship or boat for the purpose of insuring the proper stability, both to avoid risk of capsizing and to secure the greatest effectiveness of the propelling power. A usual modern form of ballast is water, which is pumped in or out of compartments arranged to receive it; lead is also much used, especially for craft of moderate size, and is often run into a space left for it between the plates of the keel, or cast into plates of appropriate form and bolted to the exterior of the keel. Gravel, stones, pig-iron, and other weighty materials are in common use as ballast, in cases where the requisite weight cannot be found in the regular cargo itself.
2. n. Bags of sand placed in the car of a balloon to steady it and to enable the aëronaut to lighten the balloon, when necessary to effect a rise, by throwing part of the sand out.
3. n. Gravel, broken stones, slag, or similar material (usually called road-metal), placed between the sleepers or ties of a railroad, to prevent them from shifting, and generally to give solidity to the road. The name is also given to the stones, burnt clay, etc., used as a foundation in making new roads, laying concrete floors, etc.
4. n. Figuratively, that which gives stability or steadiness, mental, moral, or political.
5. To place ballast in or on; furnish with ballast: as, to ballast a ship; to ballast a balloon; to ballast the bed of a railroad. See the noun.
6. Figuratively: To give steadiness to; keep steady.
7. To serve as a counterpoise to; keep down by counteraction.
8. To load; freight.
9. To load or weigh down.
10. Ballasted.
11. n. The rough masonry of the interior of a wall, or that laid upon the vault; masonry used where weight and solidity are needed. Compare filling, 7, and back-filling.

Wiktionary

1. n. nautical Heavy material that is placed in the hold of a ship (or in the gondola of a balloon), to provide stability.
2. n. figuratively Anything that steadies emotion or the mind.
3. n. Coarse gravel or similar material laid to form a bed for roads or railroads.
4. n. construction A material, such as aggregate or precast concrete pavers, which employs its mass and the force of gravity to hold single-ply roof membranes in place.
5. n. countable, electronics device used for stabilizing current in an electric circuit (e.g.in a tube lamp supply circuit)
6. v. To stabilize or load a ship with ballast.
7. v. To lay ballast on the bed of a railroad track.

GNU Webster's 1913

1. n. (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. n. Any heavy matter put into the car of a balloon to give it steadiness.
3. n. Gravel, broken stone, etc., laid in the bed of a railroad to make it firm and solid.
4. n. The larger solids, as broken stone or gravel, used in making concrete.
5. n. Fig.: That which gives, or helps to maintain, uprightness, steadiness, and security.
6. v. To steady, as a vessel, by putting heavy substances in the hold.
7. v. To fill in, as the bed of a railroad, with gravel, stone, etc., in order to make it firm and solid.
8. v. To keep steady; to steady, morally.

WordNet 3.0

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