The Collaborative International Dictionary of English v.0.48:

Counselor \Coun"sel*or\ (koun"s[e^]l*[~e]r), n. [Written also
   counsellor.] [OE. conseiler, F. conseiller, fr. L.
   consiliarius, fr. consilium counsel.]
   1. One who counsels; an adviser.
      [1913 Webster]

            Can he that speaks with the tongue of an enemy be a
            good counselor, or no?                --Shak.
      [1913 Webster]

   2. A member of council; one appointed to advise a sovereign
      or chief magistrate.

   Note: [See under Consilor.]
         [1913 Webster]

   3. One whose profession is to give advice in law, and manage
      causes for clients in court; a barrister.

   Syn: advocate, counsel, counselor, counselor-at-law;
        attorney.
        [1913 Webster]

              Good counselors lack no clients.    --Shak.
        [1913 Webster]

   4. someone who has supervisory duties at a summer camp.
      [PJC]

WordNet (r) 3.0 (2006):

counselor
    n 1: someone who gives advice about problems [syn: counselor,
         counsellor]
    2: someone who has supervisory duties at a summer camp [syn:
       counselor, counsellor]
    3: a lawyer who pleads cases in court [syn: advocate,
       counsel, counselor, counsellor, counselor-at-law,
       pleader]