What does "rammer" mean?

Rammer: One who, or that which, rams or drives. Specifically: (a) An instrument for driving anything force; as, a rammer for driving stones or piles, or for beating the earth to more solidity. (b) A rod for forcing down the charge of a gun; a ramrod. (c) (Founding) An implement for pounding the sand of a mold to render it compact.