1. Nautical. any heavy material carried temporarily or permanently in a vessel to provide desired draft and stability.
2. 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.
3. anything that gives mental, moral, or political stability or steadiness: the ballast of a steady income.
4. gravel, broken stone, slag, etc., placed between
"railways can be ballasted."
This list can help you learn new vocabulary more quickly and be able explore other words more easily.