The Collaborative International Dictionary of English v.0.48:

Councilor \Coun"cil*or\ (koun"s?l-?r), n.
   A member of a council. [Written also councillor.]
   [1913 Webster]

   Note: The distinction between councilor, a member of a
         council, and counselor, one who gives counsel, was not
         formerly made, but is now very generally recognized and
         observed.
         [1913 Webster] councilorship

WordNet (r) 3.0 (2006):

councillor
    n 1: a member of a council [syn: council member, councillor]