The Collaborative International Dictionary of English v.0.48:

Pleader \Plead"er\, n. [F. plaideur.]
   1. One who pleads; one who argues for or against; an
      advotate.
      [1913 Webster]

            So fair a pleader any cause may gain. --Dryden.
      [1913 Webster]

   2. (Law) One who draws up or forms pleas; the draughtsman of
      pleas or pleadings in the widest sense; as, a special
      pleader.
      [1913 Webster]

WordNet (r) 3.0 (2006):

pleader
    n 1: a lawyer who pleads cases in court [syn: advocate,
         counsel, counselor, counsellor, counselor-at-law,
         pleader]