Trochoid

• POS: Adjective, Noun
• HYPHEN: tro=choid

CIDE DICTIONARY

Trochoid, n. [Gr. a wheel + -oid; cf. F. trochoïde. See Troche.].

 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.  [1913 Webster]

Trochoid, a. 

•  Admitting of rotation on an axis; -- sometimes applied to a pivot joint like that between the atlas and axis in the vertebral column.  [1913 Webster]
•  Top-shaped; having a flat base and conical spire; -- said of certain shells.  [1913 Webster]
•  Of or pertaining to the genus Trochus or family Trochidæ.  [1913 Webster]

OXFORD DICTIONARY

Trochoid, adj. & n.
--adj.
1 Anat. rotating on its own axis.
2 Geom. (of a curve) traced by a point on a radius of a circle rotating along a straight line or another circle.
--n. a trochoid joint or curve.

Derivative

trochoidal adj.

Etymology

Gk trokhoeides wheel-like f. trokhos wheel