The Collaborative International Dictionary of English v.0.48:

Advocate \Ad"vo*cate\, v. t. [imp. & p. p. Advocated; p. pr. &
   vb. n. Advocating.] [See Advocate, n., Advoke, Avow.]
   To plead in favor of; to defend by argument, before a
   tribunal or the public; to support, vindicate, or recommend
   publicly.
   [1913 Webster]

         To advocate the cause of thy client.     --Bp.
                                                  Sanderson
                                                  (1624).
   [1913 Webster]

         This is the only thing distinct and sensible, that has
         been advocated.                          --Burke.
   [1913 Webster]

         Eminent orators were engaged to advocate his cause.
                                                  --Mitford.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Advocate \Ad"vo*cate\, n. [OE. avocat, avocet, OF. avocat, fr.
   L. advocatus, one summoned or called to another; properly the
   p. p. of advocare to call to, call to one's aid; ad + vocare
   to call. See Advowee, Avowee, Vocal.]
   1. One who pleads the cause of another. Specifically: One who
      pleads the cause of another before a tribunal or judicial
      court; a counselor.
      [1913 Webster]

   Note: In the English and American Law, advocate is the same
         as "counsel," "counselor," or "barrister." In the civil
         and ecclesiastical courts, the term signifies the same
         as "counsel" at the common law.
         [1913 Webster]

   2. One who defends, vindicates, or espouses any cause by
      argument; a pleader; as, an advocate of free trade, an
      advocate of truth.
      [1913 Webster]

   3. Christ, considered as an intercessor.
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            We have an Advocate with the Father.  --1 John ii.
                                                  1.
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   Faculty of advocates (Scot.), the Scottish bar in
      Edinburgh.

   Lord advocate (Scot.), the public prosecutor of crimes, and
      principal crown lawyer.

   Judge advocate. See under Judge.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Advocate \Ad"vo*cate\, v. i.
   To act as advocate. [Obs.] --Fuller.
   [1913 Webster]

WordNet (r) 3.0 (2006):

advocate
    n 1: a person who pleads for a cause or propounds an idea [syn:
         advocate, advocator, proponent, exponent]
    2: a lawyer who pleads cases in court [syn: advocate,
       counsel, counselor, counsellor, counselor-at-law,
       pleader]
    v 1: push for something; "The travel agent recommended strongly
         that we not travel on Thanksgiving Day" [syn: recommend,
         urge, advocate]
    2: speak, plead, or argue in favor of; "The doctor advocated a
       smoking ban in the entire house" [syn: preach, advocate]

Moby Thesaurus II by Grady Ward, 1.0:

260 Moby Thesaurus words for "advocate":
   Maecenas, abet, abettor, acquaintance, admirer, advance, advise,
   aficionado, agent, aid and abet, allege in support, alpenstock,
   alter ego, alternate, amicus curiae, angel, answer, apologete,
   apologist, apologizer, argue for, arm, assert, athletic supporter,
   attorney, attorney-at-law, back, backbone, backer, backing,
   backstop, backup, backup man, bandeau, barrister, barrister-at-law,
   bearer, best friend, blandish, boost, bosom friend, bra, brace,
   bracer, bracket, brassiere, brief, brother, buff, buttress, cajole,
   call on, call upon, cane, carrier, casual acquaintance, cervix,
   champion, close acquaintance, close friend, coach, coax, comfort,
   commend, confer, confidant, confidante, consult with, contend for,
   corset, counsel, counselor, counselor-at-law, countenance, counter,
   crook, crutch, cry up, defend, defender, dependence, deputy,
   direct, dummy, embolden, encourage, encourager, endorse, endorser,
   espouse, executive officer, exhort, exponent, expounder, familiar,
   fan, favor, favorer, fellow, fellow creature, fellowman,
   figurehead, forward, foundation garment, friend, friend at court,
   fulcrum, girdle, go for, guard, guide, guy, guywire, hearten,
   high-pressure, hype, importune, inseparable friend, insist,
   insist upon, instruct, intercessor, intimate, jawbone, jock,
   jockstrap, justifier, justify, keep in countenance, kibitz, lawyer,
   legal adviser, legal counselor, legal expert, legal practitioner,
   legalist, lieutenant, lobby, locum, locum tenens, lover, mainstay,
   maintain, maintainer, make a plea, mast, meddle, mouthpiece, nag,
   neck, neighbor, other self, paladin, paranymph, partisan, patron,
   pickup, pinch hitter, plead for, plead with, pleader, plug,
   prescribe, press, pressure, proctor, procurator, promote, promoter,
   prop, proponent, propose, protagonist, protector, proxy, puff,
   push, rebut, recommend, refute, reinforce, reinforcement,
   reinforcer, reliance, reply, repository, representative, respond,
   rest, resting place, rigging, riposte, say in defense, sea lawyer,
   second, second in command, secondary, seconder, sectary,
   self-styled lawyer, shine upon, shoulder, shroud, side with, sider,
   smile upon, soft-soap, solicitor, speak for, speak highly of,
   speak up for, speak warmly of, speak well of, spine, sponsor,
   sprit, staff, stalwart, stand behind, stand up for, stand-in,
   standby, standing rigging, stave, stay, stick, stick up for,
   stiffener, strengthener, submit, subscribe, substitute,
   successful advocate, suggest, support, supporter, surrogate,
   sustain, sustainer, sweet-talk, sympathizer, tout, understudy,
   uphold, upholder, urge, urge reasons for, utility man, vicar,
   vicar general, vice, vicegerent, vindicate, vindicator, votary,
   walking stick, well-wisher, wheedle, whitewasher, work on



Easton's 1897 Bible Dictionary:

Advocate
   (Gr. parakletos), one who pleads another's cause, who helps
   another by defending or comforting him. It is a name given by
   Christ three times to the Holy Ghost (John 14:16; 15:26; 16:7,
   where the Greek word is rendered "Comforter," q.v.). It is
   applied to Christ in 1 John 2:1, where the same Greek word is
   rendered "Advocate," the rendering which it should have in all
   the places where it occurs. Tertullus "the orator" (Acts 24:1)
   was a Roman advocate whom the Jews employed to accuse Paul
   before Felix.


Bouvier's Law Dictionary, Revised 6th Ed (1856):

ADVOCATE, civil and ecclesiastical law. 1. An officer who maintains or de
fends the rights of his client in the same manner as the counsellor does in
the common law.
     2. Lord Advocate. An, officer of state in Scotland, appointed by the
king, to advise about the making and executing the law, to prosecute capital
crimes, &c.
     3. College or faculty of advocates. A college consisting of 180
persons, appointed to plead in. all actions before the lords of sessions.
     4. Church or ecclesiastical advocates. Pleaders appointed by the church
to maintain its rights.
     5.-2. A patron who has the advowson or presentation to a church.
Tech. Dict.; Ayl. Per. 53; Dane Ab. c.,31, Sec. 20. See Counsellor at law;
Honorarium.