The Collaborative International Dictionary of English v.0.48:

Gang \Gang\ (g[a^]ng), v. i. [AS. gangan, akin to OS. & OHG.
   gangan, Icel. ganga, Goth. gaggan; cf. Lith. [zdot]engti to
   walk, Skr. ja[.n]gha leg. [root]48. Cf. Go.]
   To go; to walk.
   [1913 Webster]

   Note: Obsolete in English literature, but still used in the
         North of England, and also in Scotland.
         [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Gang \Gang\, n. [Icel. gangr a going, gang, akin to AS., D., G.,
   & Dan. gang a going, Goth. gaggs street, way. See Gang, v.
   i.]
   1. A going; a course. [Obs.]
      [1913 Webster]

   2. A number going in company; hence, a company, or a number
      of persons associated for a particular purpose; a group of
      laborers under one foreman; a squad; as, a gang of
      sailors; a chain gang; a gang of thieves.
      [1913 Webster]

   3. A combination of similar implements arranged so as, by
      acting together, to save time or labor; a set; as, a gang
      of saws, or of plows.
      [1913 Webster]

   4. (Naut.) A set; all required for an outfit; as, a new gang
      of stays.
      [1913 Webster]

   5. [Cf. Gangue.] (Mining) The mineral substance which
      incloses a vein; a matrix; a gangue.
      [1913 Webster]

   6. A group of teenagers or young adults forming a more or
      less formalized group associating for social purposes, in
      some cases requiring initiation rites to join; as, a teen
      gang; a youth gang; a street gang.

   Note: Youth gangs often associate with particular areas in a
         city, and may turn violent when they feel their
         territory is encroached upon. In Los Angeles the
         Crips and the Bloods are large gangs antagonistic
         to each other.
         [PJC]

   7. A group of persons organized for criminal purposes; a
      criminal organization; as, the Parker gang.
      [PJC]

   Gang board, or Gang plank. (Naut.)
      (a) A board or plank, with cleats for steps, forming a
          bridge by which to enter or leave a vessel.
      (b) A plank within or without the bulwarks of a vessel's
          waist, for the sentinel to walk on.

   Gang cask, a small cask in which to bring water aboard
      ships or in which it is kept on deck.

   Gang cultivator, Gang plow, a cultivator or plow in which
      several shares are attached to one frame, so as to make
      two or more furrows at the same time.

   Gang days, Rogation days; the time of perambulating
      parishes. See Gang week (below).

   Gang drill, a drilling machine having a number of drills
      driven from a common shaft.

   Gang master, a master or employer of a gang of workmen.

   Gang plank. See Gang board (above).

   Gang plow. See Gang cultivator (above).

   Gang press, a press for operating upon a pile or row of
      objects separated by intervening plates.

   Gang saw, a saw fitted to be one of a combination or gang
      of saws hung together in a frame or sash, and set at fixed
      distances apart.

   Gang tide. See Gang week (below).

   Gang tooth, a projecting tooth. [Obs.] --Halliwell.

   Gang week, Rogation week, when formerly processions were
      made to survey the bounds of parishes. --Halliwell.

   Live gang, or Round gang, the Western and the Eastern
      names, respectively, for a gang of saws for cutting the
      round log into boards at one operation. --Knight.

   Slabbing gang, an arrangement of saws which cuts slabs from
      two sides of a log, leaving the middle part as a thick
      beam.
      [1913 Webster] gangboard

WordNet (r) 3.0 (2006):

gang
    n 1: an association of criminals; "police tried to break up the
         gang"; "a pack of thieves" [syn: gang, pack, ring,
         mob]
    2: an informal body of friends; "he still hangs out with the
       same crowd" [syn: crowd, crew, gang, bunch]
    3: an organized group of workmen [syn: gang, crew, work
       party]
    4: tool consisting of a combination of implements arranged to
       work together
    v 1: act as an organized group [syn: gang, gang up]

Moby Thesaurus II by Grady Ward, 1.0:

175 Moby Thesaurus words for "gang":
   Bund, Rochdale cooperative, affiliate, age group, alliance, ally,
   army, assemblage, associate, association, axis, band,
   band together, battalion, be in cahoots, bevy, bloc, body, brigade,
   bunch, bunch up, cabal, cast, cement a union, centralize, circle,
   clique, club, club together, coalition, cohort, college, colony,
   combination, combine, come together, common market, commute,
   company, complement, confederacy, confederate, confederation,
   consociate, conspire, consumer cooperative, contingent,
   cooperative, cooperative society, corps, coterie, council, couple,
   course, cover ground, covey, credit union, crew, crowd,
   customs union, detachment, detail, division, drift, drive, drove,
   economic community, employees, faction, fare, fare forth,
   federalize, federate, federation, fetch, fleet, flit, flock, flow,
   force, free trade area, gam, gang up, go, go along, go in partners,
   go in partnership, group, grouping, groupment, help, herd, hie,
   hired help, hook up with, host, in-group, join forces,
   join fortunes with, join together, join up with, join with, junta,
   kennel, league, litter, machine, marry, men, mob, move, move along,
   move on, movement, organize, out-group, outfit, overwhelm, pack,
   pair, pair off, partner, partnership, party, pass, peer group,
   personnel, phalanx, platoon, pod, political machine, posse, pride,
   progress, regiment, retinue, ring, roll, roll on, run, salon,
   sashay, school, servantry, set, shoal, skulk, sloth, society,
   squad, stable, staff, stand together, stand up with, stream,
   string, team, team up with, team with, the help, throw in with,
   tie in with, tie up with, travel, tribe, trip, troop, troupe,
   union, unionize, unite with, wayfare, wed, wend, wing