Typically handsome and/or sexy, an Illumator is an individual who works in the art of Illumation. All right wise guy, what's Illumation then? Illumation is of course the process of using moving illustrations to create a story. You're probably saying, that sounds an awful lot like animation. The difference between them is based on the two elements that affect all things: technique and time. Animation requires that the sketches and illustrations are developed to create fluid motion between the gaps in say a character's position. This requires a great deal of time and usually enough talented people that don't have day jobs to sit all day and make sure the production comes together. Illumation rather, decides to ignore the gaps and simply shifts the character into the desired position without using any separate drawings in between. Illumation is basically an animatic but that the finished product IS the finished product instead of being a stage in an animation production.
Think of it like the difference between a character drawn on a piece of paper, cut out, and pasted on a Popsicle stick versus a sock puppet. The sock puppet can be made to move and talk with fluid motion whereas the cutout puppet can be used to tell the same story just by waving the damn thing around.
So the difference between an Animator and an Illumator is this: Illumators have day jobs and don't like their hands smelling like feet.