The Collaborative International Dictionary of English v.0.48:

Essayist \Es"say*ist\ (?; 277), n.
   A writer of an essay, or of essays. --B. Jonson.
   [1913 Webster]

WordNet (r) 3.0 (2006):

essayist
    n 1: a writer of literary works [syn: essayist, litterateur]

Moby Thesaurus II by Grady Ward, 1.0:

60 Moby Thesaurus words for "essayist":
   advertising writer, annalist, art critic, author, authoress,
   belletrist, bibliographer, coauthor, collaborator, columnist,
   compiler, composer, copywriter, creative writer, critic,
   dance critic, descanter, diarist, discourser, disquisitor,
   drama critic, dramatist, encyclopedist, expositor, free lance,
   free-lance writer, ghost, ghostwriter, humorist, inditer,
   literary artist, literary craftsman, literary critic, literary man,
   litterateur, logographer, magazine writer, man of letters,
   monographer, monographist, music critic, newspaperman, novelettist,
   novelist, pamphleteer, penwoman, poet, prose writer, reviewer,
   scenario writer, scenarist, scribe, scriptwriter,
   short-story writer, storyteller, technical writer, tractation,
   word painter, wordsmith, writer