The Collaborative International Dictionary of English v.0.48:

Author \Au"thor\ ([add]"th[~e]r), n. [OE. authour, autour, OF.
   autor, F. auteur, fr. L. auctor, sometimes, but erroneously,
   written autor or author, fr. augere to increase, to produce.
   See Auction, n.]
   1. The beginner, former, or first mover of anything; hence,
      the efficient cause of a thing; a creator; an originator.
      [1913 Webster]

            Eternal King; thee, Author of all being. --Milton.
      [1913 Webster]

   2. One who composes or writes a book; a composer, as
      distinguished from an editor, translator, or compiler.
      [1913 Webster]

            The chief glory of every people arises from its
            authors.                              --Johnson.
      [1913 Webster]

   3. The editor of a periodical. [Obs.]
      [1913 Webster]

   4. An informant. [Archaic] --Chaucer.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Author \Au"thor\ ([add]"th[~e]r), v. t.
   1. To occasion; to originate. [Obs.]
      [1913 Webster]

            Such an overthrow . . . I have authored. --Chapman.
      [1913 Webster]

   2. To tell; to say; to declare. [Obs.]
      [1913 Webster]

            More of him I dare not author.        --Massinger.
      [1913 Webster]

WordNet (r) 3.0 (2006):

author
    n 1: writes (books or stories or articles or the like)
         professionally (for pay) [syn: writer, author]
    2: someone who originates or causes or initiates something; "he
       was the generator of several complaints" [syn: generator,
       source, author]
    v 1: be the author of; "She authored this play"

Moby Thesaurus II by Grady Ward, 1.0:

184 Moby Thesaurus words for "author":
   actor, advertising writer, agent, ancestor, ancestors, annalist,
   apprentice, architect, art critic, artificer, artist, authoress,
   bear, beget, begetter, beginner, belletrist, bibliographer, breed,
   bring about, bring forth, bring to effect, bring to pass, builder,
   catalyst, cause, causer, coauthor, collaborate, collaborator,
   columnist, compiler, compose, composer, conceive, conceiver,
   constructor, copywriter, craftsman, create, creative writer,
   creator, critic, dance critic, dash off, descanter, designer,
   deviser, diarist, discourser, discoverer, disquisitor, do, doer,
   drama critic, dramatist, editorialize, effect, effector,
   effectuate, encyclopedist, engender, engenderer, engineer,
   essayist, establish, executant, executor, executrix, expositor,
   fabricator, father, formulate, found, founder, framer, free lance,
   free-lance, free-lance writer, generate, generator, gestate, ghost,
   ghostwrite, ghostwriter, give birth to, give occasion to,
   give origin to, give rise to, grower, humorist, inaugurate,
   inaugurator, indite, inditer, industrialist, initiator, inspirer,
   instigator, institute, institutor, introducer, inventor,
   journeyman, knock off, knock out, literary artist,
   literary craftsman, literary critic, literary man, litterateur,
   logographer, magazine writer, make, maker, man of letters,
   manufacturer, master, master craftsman, medium, monographer,
   monographist, mother, mover, music critic, newspaperman,
   novelettist, novelist, novelize, occasion, operant, operative,
   operator, organizer, origin, originate, originator, pamphleteer,
   parent, past master, patriarch, penwoman, performer, perpetrator,
   planner, poet, practitioner, precursor, prepare, prime mover,
   primum mobile, procreator, produce, producer, prose writer, raiser,
   realize, realizer, reviewer, scenario writer, scenarist, scenarize,
   scribe, scriptwriter, set afloat, set on foot, set up, shaper,
   short-story writer, sire, smith, source, storyteller, subject,
   technical writer, throw on paper, tractation, word painter,
   wordsmith, work, worker, wright, write, writer