writer

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun One who writes, especially as an occupation.

from The Century Dictionary.

• noun A person who understands or practises the art of writing; one who is able to write; a penman.
• noun One who does writing as a business; a professional scribe, scrivener, or amanuensis: used specifically in England of clerks to the former East India Company, and of temporary copying clerks in government offices; in Scotland, loosely, of law agents, solicitors, attorneys, etc., and sometimes of their principal clerks.
• noun A person who writes what he composes in his mind; the author of a written paper or of writings; an author in general; a literary producer of any kind: as, the writer of a letter; a writer of history or of fiction.

from the GNU version of the Collaborative International Dictionary of English.

• noun One who writes, or has written; a scribe; a clerk.
• noun One who is engaged in literary composition as a profession; an author.
• noun A clerk of a certain rank in the service of the late East India Company, who, after serving a certain number of years, became a factor.
• noun (Med.) a painful spasmodic affection of the muscles of the fingers, brought on by excessive use, as in writing, violin playing, telegraphing, etc. Called also scrivener's palsy.
• noun See under Signet.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun A person who writes, or produces literary work.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun a person who is able to write and has written something
• noun writes (books or stories or articles or the like) professionally (for pay)