What is Seabiscuit in the title of 2003 film?

Answer 1

only one horse;

Actually, "Seabiscuit" was portrayed by fifteen different horses. All were handpicked by retired jockey Chris McCarron, a consultant on the film. Different horses were needed for different scenes and behaviors such as racing, close-ups, lying down, acting -up,etc.

A mechanical horse was also used for trick shots.

That's Hollywood !

Answer 2

Seabiscuit is the four-legged star in the film. The Thoroughbred race horse from the depression era, his rise from obscurity and the three supporting players in his life, Charles Howard (owner), Tom Smith (trainer), and Red Pollard (jockey).