Definition of "trochoid" []

• A curve traced by a point on or connected with a circle as the circle rolls along a fixed straight line. (noun)
• Capable of or exhibiting rotation about a central axis. (adjective)
• Permitting rotation, as a pulley or pivot. (adjective)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "In one form, the ginglymus, this axis is, practically speaking, transverse; in the other, the trochoid or pivot-joint, it is longitudinal."
• "—This articulation is a trochoid or pivot-joint between the circumference of the head of the radius and the ring formed by the radial notch of the ulna and the annular ligament."