柯林斯詞典ballast /?b?l?st/ 1. N-UNCOUNT 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. 壓艙物 返回 ballast劍橋詞典heavy matter such as sand or stone that is used at the bottom of a ship or a hot-air balloon to make it heavier , or the small stones on which railways and roads are made （船的）壓艙物；（氣球的）鎮(zhèn)重物；（用作路基的）道砟，石碴 返回 ballast