All horses have a "fast" gait! A gallop is a fast gait...
Gallop
The speed depends on the horse and the gait. Here is the speed of an average horse in each main gait: === ===
A gait is something a horse does, such as gallop and jump. There is no horse that is a gait.
Slow down to a walk and keep him in that gait.
The horse gait that starts with a 'p' is called Piaffe.
Skip is not a horse gait
The walk is the slowest gait. The walk is the horse's slowest gait.
Yes Canter is a gait
'skip' is not a gait of a horse all the others are though! :)
Your question is a little misleading because a rack is a different gait from what a horse running or galloping is doing. Fast racking horses can do the smooth rack gait at 25 to 30 MPH. For some neat videos search for "The Gravedigger" or "Rowdy Rawhide's Rocket" on you tube, or just speed racking horse.
If you are actually riding the horse, you should (obviously) know which gait you are in. If not, look at how fast the horse is going, the rider's position (forward seat?) the hoof pattern etc.
Gait