He is a fast/slow 'walker'. [=he walks at a fast/slow pace]
She joined a group of 'walkers' in the neighborhood.
(..) I told him he shouldn't go so far west so soon, but he never listened. You don't look like a soldier. But I'm told you killed a white walker. I did, Your Grace. With a dagger made of dragonglass. Dragonglass? What the maesters call obsidian. I know what it is. We have it in Dragonstone. Why would obsidian kill a walker? I don't know. I've been going through all the old manuscripts hoping to find something, and all I've learned (..)2015 TvShow: Game of Thrones Title: Kill the Boy Season: 5 Episode 5