The Collaborative International Dictionary of English v.0.48:

Colleague \Col"league\ (k[o^]l"l[=e]g), n. [F. coll[`e]gue, L.
   collega one chosen at the same time with another, a partner
   in office; col- + legare to send or choose as deputy. See
   Legate.]
   A partner or associate in some civil or ecclesiastical office
   or employment. It is never used of partners in trade or
   manufactures.

   Syn: Helper; assistant; coadjutor; ally; associate;
        companion; confederate.
        [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Colleague \Col*league"\ (k[o^]l*l[=e]g"), v. t. & i.
   To unite or associate with another or with others. [R.]
   --Shak.
   [1913 Webster]

WordNet (r) 3.0 (2006):

colleague
    n 1: an associate that one works with [syn: colleague, co-
         worker, fellow worker, workfellow]
    2: a person who is member of one's class or profession; "the
       surgeon consulted his colleagues"; "he sent e-mail to his
       fellow hackers" [syn: colleague, confrere, fellow]

Moby Thesaurus II by Grady Ward, 1.0:

60 Moby Thesaurus words for "colleague":
   ace, adjunct, aide, ally, amigo, assistant, associate, bedfellow,
   bedmate, bosom buddy, brother, brother-in-arms, buddy, bunkie,
   bunkmate, butty, camarade, chamberfellow, chum, classmate,
   co-worker, coadjutor, cohort, comate, companion, company,
   compatriot, compeer, comrade, confederate, confrere, consociate,
   consort, copartner, crony, fellow, fellow member, fellow student,
   girl friend, gossip, helper, mate, messmate, old crony, pal, pard,
   pardner, partner, playfellow, playmate, roommate, schoolfellow,
   schoolmate, shipmate, side partner, sidekick, teammate, workfellow,
   yokefellow, yokemate