WordNet (r) 3.0 (2006):

screenwriter
    n 1: someone who writes screenplays [syn: screenwriter, film
         writer]

Moby Thesaurus II by Grady Ward, 1.0:

25 Moby Thesaurus words for "screenwriter":
   choreographer, comedian, dramatist, dramatizer, dramaturge, farcer,
   farceur, farceuse, farcist, gagman, joke writer, jokesmith,
   librettist, melodramatist, mimographer, monodramatist, play doctor,
   play fixer, playwright, playwriter, scenario writer, scenarioist,
   scenarist, scriptwriter, tragedian