chute
A sloping trough or tunnel guiding riders within its bounds without fixed tracks, either dry or lubricated.
Chutes are trough-like or tunnel-like structures which guide riders along a path without fixed tracks; riders move freely within the bounds of the chute, and are guided safely to the bottom. A chute may be built to follow topographic contours, or it may descend along a constructed framework. It may follow a straight path, or it may curve, bend, twist, or wind around in a helix. It can also be dry, or lubricated with water, snow, ice, oil, or bearings.
The sides of the trough or tunnel guide movement while leaving riders free within those bounds. A frame can support the descent where the route does not simply follow the ground.
A water slide uses flowing water without moving seats or boats. A flume carries its passengers in boats through a wet chute.