A relatively dense substance that is placed in the cab of a balloon and can be thrown out to reduce the load or can be shifted to change the center of gravity.

Crushed stone used in a railroad bed to support the ties, hold the track in line, and help drainage.

A circuit element that serves to limit an electric current or to provide a starting voltage, as in certain types of lamps, such as in fluorescent ceiling fixtures.

Coarse gravel used as an ingredient in concrete.

1. A relatively heavy material such as lead, iron, or water placed in a ship to ensure stability or to maintain the proper draft or trim.

2. To pump seawater into empty fuel tanks of a ship to ensure its stability or suitable draft and trim for seaworthiness.