The Collaborative International Dictionary of English v.0.48:

Dramatist \Dram"a*tist\, n. [Cf. F. dramatiste.]
   The author of a dramatic composition; a writer of plays.
   [1913 Webster]

WordNet (r) 3.0 (2006):

dramatist
    n 1: someone who writes plays [syn: dramatist, playwright]

Moby Thesaurus II by Grady Ward, 1.0:

74 Moby Thesaurus words for "dramatist":
   advertising writer, annalist, art critic, author, authoress,
   belletrist, bibliographer, choreographer, coauthor, collaborator,
   columnist, comedian, compiler, composer, copywriter,
   creative writer, critic, dance critic, dramatizer, dramaturge,
   encyclopedist, essayist, farcer, farceur, farceuse, farcist,
   free lance, free-lance writer, gagman, ghost, ghostwriter,
   humorist, inditer, joke writer, jokesmith, librettist,
   literary artist, literary craftsman, literary critic, literary man,
   litterateur, logographer, magazine writer, man of letters,
   melodramatist, mimographer, monodramatist, monographer,
   music critic, newspaperman, novelettist, novelist, pamphleteer,
   penwoman, play doctor, play fixer, playwright, playwriter, poet,
   prose writer, reviewer, scenario writer, scenarioist, scenarist,
   screenwriter, scribe, scriptwriter, short-story writer,
   storyteller, technical writer, tragedian, word painter, wordsmith,
   writer



The Devil's Dictionary (1881-1906):

DRAMATIST, n.  One who adapts plays from the French.