[bal.last] n [prob. fr. LG, of Scand origin; akin to Dan & Sw barlast ballast; perh. akin to OE baer bare & to OE hlaest load, hladan to load--more at lade] (1530) 1: a heavy substance used to improve the stability and control the draft of a ship or the ascent of a balloon
2: something that gives stability (as in character or conduct)
3: gravel or broken stone laid in a railroad bed or used in making concrete
4: a device used to provide the starting voltage or to stabilize the current in a circuit (as of a fluorescent lamp) -- in ballast of a ship: having only ballast for a load
[2]ballast vt (1538) 1: to steady or equip with or as if with ballast
2: to fill in (as a railroad bed) with ballast