From Bushwalk Australia
A saddle, or mountain pass is an area of land with a lower elevation between two areas of higher elevation, on a mountain or mountain range. Walking tracks and roads will often use the saddle to pass over a mountain, or to reach the higher areas of elevation on either side, due to the gentle gradient of the saddle. Streams also tend to form in a saddle with the water being funneled from the tops of the mountain to the top of the saddle, and down the saddle itself.
A saddle may be a small sunken area or may be a deep valley in a mountain or range, however the term is generally used to refer to the former due to it appearing similar to a horse's saddle.