The Collaborative International Dictionary of English v.0.48:

Con- \Con-\
   A prefix, fr. L. cum, signifying with, together, etc. See
   Com-.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Con \Con\, adv. [Abbrev. from L. contra against.]
   Against the affirmative side; in opposition; on the negative
   side; -- The antithesis of pro, and usually in connection
   with it. See Pro.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Con \Con\, v. t. [imp. & p. p. Conned; p. pr. & vb. n.
   Conning.] [AS. cunnan to know, be able, and (derived from
   this) cunnian to try, test. See Can, v. t. & i.]
   1. To know; to understand; to acknowledge. [Obs.]
      [1913 Webster]

            Of muses, Hobbinol, I con no skill.   --Spenser.
      [1913 Webster]

            They say they con to heaven the highway. --Spenser.
      [1913 Webster]

   2. To study in order to know; to peruse; to learn; to commit
      to memory; to regard studiously.
      [1913 Webster]

            Fixedly did look
            Upon the muddy waters which he conned
            As if he had been reading in a book.  --Wordsworth.
      [1913 Webster]

            I did not come into Parliament to con my lesson.
                                                  --Burke.
      [1913 Webster]

   To con answer, to be able to answer. [Obs.]

   To con thanks, to thank; to acknowledge obligation. [Obs.]
      --Shak.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Con \Con\, v. t. [See Cond.] (Naut.)
   To conduct, or superintend the steering of (a vessel); to
   watch the course of (a vessel) and direct the helmsman how to
   steer.
   [1913 Webster]

WordNet (r) 3.0 (2006):

con
    adv 1: in opposition to a proposition, opinion, etc.; "much was
           written pro and con" [ant: pro]
    n 1: an argument opposed to a proposal [ant: pro]
    2: a person serving a sentence in a jail or prison [syn:
       convict, con, inmate, yard bird, yardbird]
    3: a swindle in which you cheat at gambling or persuade a person
       to buy worthless property [syn: bunco, bunco game,
       bunko, bunko game, con, confidence trick, confidence
       game, con game, gyp, hustle, sting, flimflam]
    v 1: deprive of by deceit; "He swindled me out of my
         inheritance"; "She defrauded the customers who trusted
         her"; "the cashier gypped me when he gave me too little
         change" [syn: victimize, swindle, rook, goldbrick,
         nobble, diddle, bunco, defraud, scam, mulct,
         gyp, gip, hornswoggle, short-change, con]
    2: commit to memory; learn by heart; "Have you memorized your
       lines for the play yet?" [syn: memorize, memorise, con,
       learn]

Moby Thesaurus II by Grady Ward, 1.0:

212 Moby Thesaurus words for "con":
   POW, adversary, adversative, adverse, against, alien, antagonistic,
   anti, antipathetic, antithetic, argue into, argument, argumentum,
   aye, beat, beguile of, bilk, bone, bring over, bring round,
   bring to reason, bunco, burn, cageling, captivate, captive, case,
   chain gang, charm, cheat, chisel, chouse, chouse out of, clashing,
   cog, cog the dice, commit to memory, competitive, conflicting,
   cons, consideration, contemplate, contradictory, contrary, convict,
   convince, counter, cozen, crib, cross, defraud, detenu, diddle,
   dig, disaccordant, disappointed, disapprobatory, disapproving,
   discontented, disenchanted, disgruntled, disillusioned, displeased,
   dissatisfied, dissentient, dissenting, do in, do out of, draw over,
   drill, elenchus, elucubrate, enemy, euchre, ex-convict, examine,
   finagle, flam, fleece, flimflam, fob, fractious, fudge, gain,
   gain over, gaolbird, get by heart, get letter-perfect, go over,
   gouge, grind, gull, gyp, have, have by heart, hocus, hocus-pocus,
   hook, hook in, hostile, ignoratio elenchi, indignant, inimical,
   interest, internee, jailbird, know by heart, learn by heart,
   learn verbatim, lifer, low, lucubrate, memorize, mulct, nay,
   negative, no, noncooperative, obstinate, opponent, opposed,
   opposing, opposite, oppositional, oppositive, oppugnant, outtalk,
   overthwart, pack the deal, parolee, parrot, persuade, peruse,
   perverse, pigeon, plaidoyer, plea, pleading, plunge into,
   political prisoner, poor, pore over, practice, practice fraud upon,
   prevail on, prevail upon, prevail with, prisoner, prisoner of war,
   pro, pros, pros and cons, read, reason, recalcitrant, recite,
   refractory, refutation, regard studiously, repeat, repeat by heart,
   repugnant, restudy, review, rival, rook, scam, screw, sell,
   sell gold bricks, sell one on, shave, shortchange, side,
   special pleading, stack the cards, stick, sting, stir bird, study,
   sway, swindle, swot, swot up, take a dive, talk into, talk over,
   talking point, the affirmative, the negative, thimblerig,
   throw a fight, ticket-of-leave man, ticket-of-leaver, trusty,
   turned-off, unappreciative, unapproving, uncomplimentary,
   uncooperative, unfavorable, unfriendly, unhappy, unpropitious, vet,
   victimize, wade through, wangle, wangle into, wear down, win,
   win over



The Jargon File (version 4.4.7, 29 Dec 2003):

con
 n.

    [from SF fandom] A science-fiction convention. Not used of other sorts of
    conventions, such as professional meetings. This term, unlike many others
    imported from SF-fan slang, is widely recognized even by hackers who aren't
    fans. ?We'd been corresponding on the net for months, then we met
    face-to-face at a con.?