ballast

The definition of ballast is something that provides security and balance.

(noun)

An example of ballast for some people is their belief in God.
An example of ballast on a boat is gravel used to balance or make the boat stable.
An example of ballast is bags of sand in a hot air balloon.

See ballast in Webster's New World College Dictionary

noun

anything heavy carried in a ship, aircraft, or vehicle to give stability or in a balloon or airship to help control altitude
anything giving stability and firmness to character, human relations, etc.
crushed rock or gravel, as that placed between and below railroad ties

Origin: LowG < MDu < bal, bad, useless (akin to OE bealu, bale) + last, a load

transitive verb

See ballast in American Heritage Dictionary 4

noun

Heavy material that is placed in the hold of a ship or the gondola of a balloon to enhance stability.
a. Coarse gravel or crushed rock laid to form a bed for roads or railroads.
b. The gravel ingredient of concrete.
Something that gives stability, especially in character.

transitive verb bal·last·ed, bal·last·ing, bal·lasts