adj. 外摆线的

Epicycloidal \Ep`i*cy*cloid"al\, a.
Pertaining to the epicycloid, or having its properties.

{Epicycloidal wheel}, a device for producing straight-line
motion from circular motion, on the principle that a pin
fastened in the periphery of a gear wheel will describe a
straight line when the wheel rolls around inside a fixed
internal gear of twice its diameter.