Trochoid

1. a. Of or pertaining to the genus Trochus or family Trochidae.
2. n. 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.
3. a. Admitting of rotation on an axis; — sometimes applied to a pivot joint like that between the atlas and axis in the vertebral column.
4. a. Top-shaped; having a flat base and conical spire; — said of certain shells.

The word meanings were obtained from OPTED(The Online Plain Text English Dictionary), which is based on “The Project Gutenberg Etext of Webster’s Unabridged Dictionary” which is in turn based on the 1913 US Webster’s Unabridged Dictionary (See Project Gutenburg), as a text file.