The Collaborative International Dictionary of English v.0.48:

Guild \Guild\, n. [OE. gilds, AS. gild, gield, geld, tribute, a
   society or company where payment was made for its charge and
   support, fr. AS. gildan, gieldan, to pay. See Yield, v. t.]
   1. An association of men belonging to the same class, or
      engaged in kindred pursuits, formed for mutual aid and
      protection; a business fraternity or corporation; as, the
      Stationers' Guild; the Ironmongers' Guild. They were
      originally licensed by the government, and endowed with
      special privileges and authority.
      [1913 Webster]

   2. A guildhall. [Obs.] --Spenser.
      [1913 Webster]

   3. A religious association or society, organized for
      charitable purposes or for assistance in parish work.
      [1913 Webster]

WordNet (r) 3.0 (2006):

guild
    n 1: a formal association of people with similar interests; "he
         joined a golf club"; "they formed a small lunch society";
         "men from the fraternal order will staff the soup kitchen
         today" [syn: club, social club, society, guild,
         gild, lodge, order]

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

GUILD. A fraternity or company. Guild hall, the place of meeting of guilds.
Beame's, Glanville, 108 (n).