To get off a horse, bicycle, or motorcycle. (Cambridge Dictionary)
Get off a horse, bicycle, or anything that one is riding. (Oxford Dictionaries)
Cause to fall off a horse, bicycle, etc. (Oxford Dictionaries)
To throw down or remove from a mount or an elevated position. (Merriam – Webster)
If you dismount from a horse or a bicycle, you get down from it. (Collins Dictionary)
Learn How To Dismount from a Horse.
Dismount and Light.