noun
ballast (for ships, submarines, balloons)
Used for weight added to stabilize a vessel or aircraft, such as water in submarine tanks or sandbags in a hot-air balloon.
潜水艦はバラストタンクに水を入れて潜行する。
The submarine submerges by taking water into its ballast tanks.
熱気球はバラストを捨てて上昇した。
The hot-air balloon ascended by dropping ballast.
noun
ballast (for road or railway foundations)
Refers to the layer of gravel or crushed stone placed under railway tracks or road surfaces to provide stability and drainage.
線路のバラストは定期的に交換が必要だ。
The ballast on the railway track needs to be replaced periodically.