The Collaborative International Dictionary of English v.0.48:

Mulct \Mulct\, n. [L. mulcta, multa.]
   1. A fine or penalty, esp. a pecuniary punishment or penalty.
      [1913 Webster]

   2. A blemish or defect. [Obs.]
      [1913 Webster]

   Syn: Amercement; forfeit; forfeiture; penalty.
        [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Mulct \Mulct\, v. t. [imp. & p. p. Mulcted; p. pr. & vb. n.
   Mulcting.] [L. mulctare, multare.]
   1. To punish for an offense or misdemeanor by imposing a fine
      or forfeiture, esp. a pecuniary fine; to fine.
      [1913 Webster]

   2. Hence, to deprive of; to withhold by way of punishment or
      discipline. [Obs.]
      [1913 Webster] Mulctary

WordNet (r) 3.0 (2006):

mulct
    n 1: money extracted as a penalty [syn: fine, mulct,
         amercement]
    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: impose a fine on; "he was fined for littering"

Moby Thesaurus II by Grady Ward, 1.0:

70 Moby Thesaurus words for "mulct":
   amerce, amercement, beat, beguile of, bilk, bleed, bunco, burn,
   cheat, chisel, chouse, chouse out of, claim, cog, cog the dice,
   con, cozen, crib, damages, defraud, demand, diddle, distrain,
   distraint, distress, do in, do out of, escheat, escheatment,
   estreat, euchre, exact, finagle, fine, flam, fleece, flimflam, fob,
   forfeit, forfeiture, fudge, gouge, gull, gyp, have, hocus,
   hocus-pocus, levy a distress, milk, pack the deal, penalty, pigeon,
   practice fraud upon, require, rook, scam, sconce, screw,
   sell gold bricks, shave, shortchange, stack the cards, stick,
   sting, sweat, swindle, take a dive, thimblerig, throw a fight,
   victimize



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

MULCT, punishment. A fine imposed on the conviction of an offence.



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

MULCT, commerce. An imposition laid on ships or goods by a company of trade,
for the maintenance of consuls and the like. Obsolete.