The Samyang 85mm T1.5 Cine Lens featured a "De-clicked" aperture control ring. What exactly is it?
It means the aperture ring does not have detents or, if it does, there are no audible clicks.
This is intended for video shooting as it does not make any noise when turning the aperture ring. Depending on how the lens is designed, the aperture may be stepped or not. If it is not stepped, it usual says continuous aperture or something similar.