<p><strong>Noun</strong></p><ul><li>Nautical: any heavy material carried temporarily or permanently in a vessel to provide desired draft and stability.</li><li>Aeronautics: something heavy, as bags of sand, placed in the car of a balloon for control of altitude and, less often, of attitude, or placed in an aircraft to control the position of the center of gravity.</li><li>anything that gives mental, moral, or political stability or steadiness: the ballast of a steady income.</li><li>gravel, broken stone, slag, etc., placed between and under the ties of a railroad to give stability, provide drainage, and distribute loads.</li><li>Electricity: a device, often a resistor, that maintains the current in a circuit at a constant value by varying its resistance in order to counteract changes in voltage.</li><li>a device that maintains the current through a fluorescent or mercury lamp at the desired constant value, sometimes also providing the necessary starting voltage and current.</li></ul><p><strong>Verb</strong></p><ul><li>to furnish with ballast: to ballast a ship.</li><li>to give steadiness to; keep steady: parental responsibilities that ballast a person.</li></ul>