ballasts

Heavy material placed in a ship or hot-air balloon to improve stability.

"The ship needed more ballasts for stability."

Crushed stone or gravel forming the bed for railway tracks.

"Workers replaced the old railway ballasts."

To provide something with ballast, making it stable or heavy.

"The engineer ballasts the structure carefully."

Electrical devices limiting current in fluorescent lamps.

"Faulty ballasts caused the office lights to flicker."