One who rocks; specifically, one who rocks a cradle.

One of the curving pieces of wood or metal on which a
cradle, chair, etc., rocks.

Any implement or machine working with a rocking motion, as
a trough mounted on rockers for separating gold dust from gravel, etc.,
by agitation in water.

A play horse on rockers; a rocking-horse.

A chair mounted on rockers; a rocking-chair.

A skate with a curved blade, somewhat resembling in shape
the rocker of a cradle.

Same as Rock shaft.