Positive-caster

noun, Automotive.
1.
See under (def 6).
[kas-ter, kah-ster] /ˈkæs tər, ˈkɑ stər/
noun, Also, (for defs 2–5).
1.
a person or thing that .
2.
a small wheel on a swivel, set under a piece of furniture, a machine, etc., to facilitate moving it.
3.
a bottle or cruet for holding a condiment.
4.
a stand containing a set of such bottles.
5.
a metal container for sugar, pepper, etc., having a perforated top to permit sprinkling; dredger; muffineer.
6.
Automotive. the angle that the kingpin makes with the vertical. Automobiles are usually designed with the upper end of the kingpin inclined rearward (positive caster) for improved directional stability.
verb (used without object)
7.
(of a wheel) to swivel freely in a horizontal plane.
/ˈkɑːstə/
noun
1.
a person or thing that casts
2.
Also castor. a bottle with a perforated top for sprinkling sugar, etc, or a stand containing such bottles
3.
Also castor. a small wheel mounted on a swivel so that the wheel tends to turn into its plane of rotation
n.

“person or thing that casts,” late 14c. (also sometimes castor), agent noun from cast (v.). Meaning “pepper shaker, small perforated container” is from 1670s, on notion of “throwing.”

“wheel and swivel attached to furniture,” 1748, agent noun from cast (v.) in the old sense of “turn.” Also sometimes castor.