grader

from WordNet (r) 3.0 (2006)

grader
    n 1: a judge who assigns grades to something

from The Collaborative International Dictionary of English v.0.48

Grader \Grad"er\, n.
   1. One who grades, or that by means of which grading is done
      or facilitated.

   2. Specifically: A vehicle used for levelling earth, esp. one
      with a plow blade suspended from the center, used
      specifically for grading roads.
      [PJC]