Trochoid
Trochoid , noun
[Greek {not transcribed} a wheel + -oid; compare French trochoide. See Troche.]
(Geometry) The curve described by any point in a wheel rolling on a line; a cycloid; a roulette; in general, the curve described by any point fixedly connected with a moving curve while the moving curve rolls without slipping on a second fixed curve, the curves all being in one plane. Cycloids, epicycloids, hypocycloids, cardioids, etc., are all trochoids.
Trochoid , adjective
1.
(Anatomy) Admitting of rotation on an axis; -- sometimes applied to a pivot joint like that between the atlas and axis in the vertebral column.
2.
(Zoology) Top-shaped; having a flat base and conical spire; -- said of certain shells.
3.
(Zoology) Of or pertaining to the genus Trochus or family Trochidae.