**Cy"cloid** (s?"kloid), n. [*Cyclo-* + *-oid*: cf. F. *cycloide*.] Geom.

A curve generated by a point in the plane of a circle when the circle is rolled along a straight line, keeping always in the same plane.

⇒ The *common cycloid* is the curve described when the generating point (*p*) is on the circumference of the generating circle; the *curtate cycloid*, when that point lies without the circumference; the *prolate* or *inflected cycloid*, when the generating point (*p*) lies within that circumference.

© Webster 1913.

**Cy"cloid**, a. Zool.

Of or pertaining to the Cycloidei.

Cycloid scale Zool., a fish scale which is thin and shows concentric lines of growth, without serrations on the margin.

© Webster 1913.

**Cy"cloid**, n. Zool.

One of the Cycloidei.

© Webster 1913.