speaker

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

• noun One who speaks.
• noun A spokesperson.
• noun One who delivers a public speech.
• noun The presiding officer of a legislative assembly.
• noun A device that converts electric signals to audible sound.

from The Century Dictionary.

• noun One who speaks or utters words; one who talks or converses; one who mates a speech or an address; specifically, one who engages in or practises public speaking.
• noun A proclaimer; a publisher.
• noun The title of the presiding officer in the British House of Commons, in the House of Representatives in the Congress of the United States, in the lower houses of State legislatures in the United States, and in British colonial legislatures; also of the Lord Chancellor of Great Britain as presiding officer of the House of Lords.
• noun A title, and hence a general name, for a book containing selections for practice in declamation, as at school.

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

• noun One who speaks.
• noun One who utters or pronounces a discourse; usually, one who utters a speech in public.
• noun One who is the mouthpiece of others; especially, one who presides over, or speaks for, a delibrative assembly, preserving order and regulating the debates
• noun United States A book of selections for declamation.

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

• noun One who speaks.
• noun Loudspeaker.
• noun politics The chair or presiding officer of certain legislative bodies, such as the U.K. House of Commons or the U.S. House of Representatives.
• noun One who makes a speech to an audience.
• noun US A book containing passages of text for use in speeches.
• noun linguistics The producer of a given utterance, whether actually spoken or not.

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

• noun electro-acoustic transducer that converts electrical signals into sounds loud enough to be heard at a distance
• noun someone who expresses in language; someone who talks (especially someone who delivers a public speech or someone especially garrulous)
• noun the presiding officer of a deliberative assembly