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The Collaborative International Dictionary of English v.0.48 (gcide)

Cycloid \Cy"cloid\ (s?"kloid), n. [Cyclo- -oid: cf. F.
cyclo["i]de.] (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.
[1913 Webster]

Note: 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.
[1913 Webster]


Cycloid \Cy"cloid\, a. (Zool.)
Of or pertaining to the Cycloidei.
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{Cycloid scale} (Zool.), a fish scale which is thin and shows
concentric lines of growth, without serrations on the
margin.
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Cycloid \Cy"cloid\, n. (Zool.)
One of the Cycloidei.
[1913 Webster]


Brachystochrone \Bra*chys"to*chrone\, n. [Incorrect for
brachistochrone, fr. Gr. bra`chistos shortest (superl. of
brachy`s short) ? time : cf. F. brachistochrone. ] (Math.)
A curve, in which a body, starting from a given point, and
descending solely by the force of gravity, will reach another
given point in a shorter time than it could by any other
path. This curve of quickest descent, as it is sometimes
called, is, in a vacuum, the same as the {cycloid}.
[1913 Webster]