A developable surface for which the set of points of intersection of the generators with each of two parallel planes $\pi_1$ and $\pi_2$ is a simple closed curve. A cylindroid is said to be closed if it is bounded by the two plane domains interior to the curves of intersection of planes $\pi_1$ and $\pi_2$ with it.
Cylindroid. Encyclopedia of Mathematics. URL: http://encyclopediaofmath.org/index.php?title=Cylindroid&oldid=31515