Webster's Revised Unabridged Dictionary · 1913

Rocker

Rocker , noun

1.
One who rocks; specifically, one who rocks a cradle.
It was I, sir, said the rocker, who had the honor, some thirty years since, to attend on your highness in your infancy. — Fuller
2.
One of the curving pieces of wood or metal on which a cradle, chair, etc., rocks.
3.
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.
4.
A play horse on rockers; a rocking-horse.
5.
A chair mounted on rockers; a rocking-chair.
6.
A skate with a curved blade, somewhat resembling in shape the rocker of a cradle.
7.
(Machinery) Same as Rock shaft.
Collocations (1)
Rocker arm (Machinery) , an arm borne by a rock shaft.