advocate

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

• intransitive verb To speak, plead, or argue in favor of: synonym: support.
• intransitive verb To act as an advocate.
• noun One that argues for a cause; a supporter or defender.
• noun One that pleads in another's behalf; an intercessor.
• noun A lawyer.

from The Century Dictionary.

• To invoke.
• To plead in favor of; defend by argument before a tribunal; support or vindicate.
• In Scots law, formerly, to transfer from an inferior court to the Court of Session, as an action while still pending, or after judgment had been given, in order that the judgment might be reviewed. See advocation, 2.
• To act as an advocate; plead.
• noun One who pleads the cause of another in a court of law; specifically, a lawyer of full rank in a country, or practising before a court, in which the civil or the canon law prevails, as France and Scotland, and the admiralty and ecclesiastical courts of England.
• noun One who defends, vindicates, or espouses a cause by argument; a pleader in favor of any person or thing; an upholder; a defender: as, an advocate of peace or of the oppressed.
• noun In the Roman Catholic Church, a name commonly applied to the promoter of the faith, one of the college of consistorial advocates in the papal court, from his office of urging the objections against the virtues, miracles, etc., of a person proposed for canonization.
• noun One given to bringing forward accusations against personal character.
• noun In England, formerly, an official who prosecuted in all criminal cases falling under military law which concerned the crown; now, a subordinate member of the government who acts as the legal adviser of the crown in all matters of military law.

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

• intransitive verb obsolete To act as advocate.
• noun One who pleads the cause of another. Specifically: One who pleads the cause of another before a tribunal or judicial court; a counselor.
• noun One who defends, vindicates, or espouses any cause by argument; a pleader.
• noun Christ, considered as an intercessor.
• noun (Scot.) the Scottish bar in Edinburgh.
• noun (Scot.) the public prosecutor of crimes, and principal crown lawyer.
• noun See under Judge.
• transitive verb To plead in favor of; to defend by argument, before a tribunal or the public; to support, vindicate, or recommend publicly.

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

• noun A person who supports others to make their voices heard, or ideally for them to speak up for themselves.
• verb transitive To argue for someone else.
• verb transitive To encourage support for something.

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

• verb push for something
• verb speak, plead, or argue in favor of
• noun a person who pleads for a cause or propounds an idea
• noun a lawyer who pleads cases in court