Dust Off A Batter Meaning

(idiomatic, baseball) for a pitcher to throw a pitch at or near the batter, typically to frighten the batter or to have him stand farther away from home plate.

Example:   That pitcher doesn't like the hitters too close to the plate so every once in a while he'll dust off a batter.
1947, Robert Smith, Baseball: a historical narrative of the game, the men who have played it, and its place in American life[1], page 206:
  He never attempted to dust off a batter; and his control was so great that no hitter was ever afraid to stand right up to the plate and look Matty's fast ball right in the eye.