a person who runs very long distances or competes in running races, such as ultramarathons, that are longer than usual races

A marathon is simply a stroll for an ultra-runner. 马拉松对于超跑者来说简直就是散步。

Perhaps the most accomplished ultrarunner ever from the United States, he completed the Barkley in 58 hours 21 minutes. 他也许是美国有史以来成就最高的超跑者，以58小时21分跑完了巴克利马拉松。