The Collaborative International Dictionary of English v.0.48:

Expel \Ex*pel"\, v. t. [imp. & p. p. Expelled, p. pr. & vb.
   n.. Expelling.] [L. expellere, expulsum; ex out + pellere
   to drive: cf.F. expeller. See Pulse a beat.]
   1. To drive or force out from that within which anything is
      contained, inclosed, or situated; to eject; as, to expel
      air from a bellows.
      [1913 Webster]

            Did not ye . . . expel me out of my father's house?
                                                  --Judg. xi. 7.
      [1913 Webster]

   2. To drive away from one's country; to banish.
      [1913 Webster]

            Forewasted all their land, and them expelled.
                                                  --Spenser.
      .
      [1913 Webster]

            He shall expel them from before you . . . and ye
            shall possess their land.             --Josh. xxiii.
                                                  5.
      [1913 Webster]

   3. To cut off from further connection with an institution of
      learning, a society, and the like; as, to expel a student
      or member.
      [1913 Webster]

   4. To keep out, off, or away; to exclude. "To expel the
      winter's flaw." --Shak.
      [1913 Webster]

   5. To discharge; to shoot. [Obs.]
      [1913 Webster]

            Then he another and another [shaft] did expel.
                                                  --Spenser.
      .

   Syn: To banish; exile; eject; drive out. See Banish.
        [1913 Webster]

WordNet (r) 3.0 (2006):

expel
    v 1: force to leave or move out; "He was expelled from his
         native country" [syn: expel, throw out, kick out]
    2: remove from a position or office; "The chairman was ousted
       after he misappropriated funds" [syn: oust, throw out,
       drum out, boot out, kick out, expel]
    3: cause to flee; "rout out the fighters from their caves" [syn:
       rout, rout out, expel]
    4: eliminate (a substance); "combustion products are exhausted
       in the engine"; "the plant releases a gas" [syn: exhaust,
       discharge, expel, eject, release]

Moby Thesaurus II by Grady Ward, 1.0:

265 Moby Thesaurus words for "expel":
   abrupt, abstract, alienate, assign, ban, banish, bar, belch,
   blackball, blow, blow off, blow out, boot, boot out, bounce, break,
   breathe, breathe hard, breathe in, breathe out, bump, bust, can,
   carry over, cashier, cast, cast forth, cast off, cast out, chuck,
   chuck out, clear, clear away, clear out, clear the decks,
   communicate, consign, cough, cut, cut adrift, cut off, cut out,
   debar, debouch, decant, deconsecrate, defenestrate, defrock,
   degrade, delete, deliver, demote, depart, deplume, deport, depose,
   deprive, dethrone, detrude, diffuse, disarticulate, disbar,
   discard, discharge, disconnect, discrown, disembogue, disemploy,
   disengage, disenthrone, disfellowship, disgorge, disjoin, disjoint,
   dislodge, dismiss, displace, displume, dispose of, dispossess,
   disseminate, dissociate, disunite, divide, divorce, drive out,
   drum out, ejaculate, eject, elide, eliminate, eradicate, eruct,
   erupt, estrange, evict, exclude, excommunicate, exhale, exhaust,
   exile, expatriate, expire, export, extradite, extravasate, extrude,
   fire, force out, fugitate, furlough, gasp, get quit of, get rid of,
   get shut of, give, give the ax, give the gate, give the hook, gulp,
   hack, hand forward, hand on, hand over, heave out, hiccup, huff,
   impart, import, inhale, inspire, irrupt, isolate, jet, jettison,
   junk, kick, kick downstairs, kick out, kick upstairs, lag, lay off,
   leave, let go, let out, liquidate, make over, make redundant,
   maroon, metastasize, metathesize, obtrude, ostracize, oust, outlaw,
   outpour, overthrow, pant, part, pass, pass on, pass over,
   pass the buck, pension, pension off, perfuse, pick out, pour,
   pour forth, pour out, proscribe, puff, pull away, pull back,
   pull out, purge, push out, put out, read out of, reject, relay,
   release, relegate, remove, remove from office, replace, respire,
   retire, root out, root up, rusticate, sack, segregate, send away,
   send down, send forth, send out, send to Coventry, separate,
   separate forcibly, sequester, set apart, set aside, show the door,
   shut off, sigh, sneeze, sniff, sniffle, snore, snort, snub, snuff,
   snuffle, spew, split, spout, spread, spurn, spurt, squirt,
   stand aloof, stand apart, stand aside, step aside, strike off,
   strike out, strip, strip of office, strip of rank, subtract,
   superannuate, surplus, suspend, switch, throw away, throw off,
   throw out, throw over, throw overboard, thrust out, toss out,
   transfer, transfer property, transfuse, translate, translocate,
   transmit, transplace, transplant, transport, transpose, turn off,
   turn out, turn over, unchurch, uncouple, unfrock, unsaddle, unseat,
   unthrone, unyoke, weed out, wheeze, withdraw