名词

1. 压舱物；镇重物
Ballast is any substance that is used in ships or hot-air balloons to make them heavier and more stable. Ballast usually consists of water, sand, or iron.

1. any heavy material used to stabilize a ship or airship

2. an electrical device for starting and regulating fluorescent and discharge lamps

Synonym: light ballast

3. a resistor inserted into a circuit to compensate for changes (as those arising from temperature fluctuations)

Synonym: ballast resistorbarretter

4. an attribute that tends to give stability in character and morals
something that steadies the mind or feelings

5. coarse gravel laid to form a bed for streets and railroads