The Collaborative International Dictionary of English v.0.48:

counsellor \counsellor\ n.
   same as counselor.

   Syn: counselor.
        [WordNet 1.5]

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):

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

Easton's 1897 Bible Dictionary:

Counsellor
   an adviser (Prov. 11:14; 15:22), a king's state counsellor (2
   Sam. 15:12). Used once of the Messiah (Isa. 9:6). In Mark 15:43,
   Luke 23:50, the word probably means a member of the Jewish
   Sanhedrim.


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

COUNSELLOR, government. A counsellor is a member of a council. In some of
the states the executive power is vested in a governor, or a governor and
lieutenant governor, and council. The members of such council are called
counsellors. See the names of the several states.