Tro″choid, a. 1. (Anat.) Admitting of rotation on an axis; — sometimes applied to a pivot joint like that between the atlas and axis in the vertebral column.
2. (Zoöl.) Top-shaped; having a flat base and conical spire; — said of certain shells.
3. (Zoöl.) Of or pertaining to the genus Trochus or family Trochidæ.