The Collaborative International Dictionary of English v.0.48:

Experimentalist \Ex*per`i*men"tal*ist\, n.
   1. One who makes experiments, especially one who likes to
      experiment; an experimenter. --Whaterly.
      [1913 Webster]

   2. One who relies primarily on experimentation and the
      evidence of one's own senses; an empiricist; -- contrasted
      with theoretician or dogmatist.
      [PJC]