Dictionary Check: ballast

any heavy material used to stabilize a ship or airship

coarse gravel laid to form a bed for streets and railroads

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

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

an electrical device for starting and regulating fluorescent and discharge lamps

make steady with a ballast