Its is called side-passing.
a crab walks sideways by sticking its claws
sideways
It uses its legs and it walks sideways
A sideways pass is called a lateral.
The word isn't specifically for a horse's legs. But the way in which someone or something walks is called a gait.
About 14.8 hands going sideways.
he's going to die
A baby that is born sideways while exiting the uterus is called a transverse presentation.
If by movement you mean tilting it is called roll. There is no name for a boat simply moving sideways.
Sidewinder
It's called "Karaoke"
a horse is a *quadruped. meaning walks on four legs. =]