The Collaborative International Dictionary of English v.0.48:

Overcharge \O`ver*charge"\, v. t. [Cf. Supercharge,
   Surcharge.]
   [1913 Webster]
   1. To charge or load too heavily; to burden; to oppress; to
      cloy. --Sir W. Raleigh.
      [1913 Webster]

   2. To fill too full; to crowd.
      [1913 Webster]

            Our language is overcharged with consonants.
                                                  --Addison.
      [1913 Webster]

   3. To charge (a buyer) an excessive price; to charge beyond a
      fair rate or price.
      [1913 Webster]

   4. To exaggerate; as, to overcharge a description.
      [1913 Webster]

   5. (Electricity) To charge (a battery) too much, so as to
      cause damage.
      [PJC]

   Overcharged mine. (Mil.) See Globe of compression, under
      Globe.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Overcharge \O`ver*charge"\, v. i.
   To make excessive charges.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Overcharge \O"ver*charge`\, n. [Cf. Supercargo,
   Supercharge.]
   [1913 Webster]
   1. An excessive load or burden.
      [1913 Webster]

   2. An excessive charge in an account.
      [1913 Webster]

WordNet (r) 3.0 (2006):

overcharge
    n 1: a price that is too high
    v 1: rip off; ask an unreasonable price [syn: overcharge,
         soak, surcharge, gazump, fleece, plume, pluck,
         rob, hook] [ant: undercharge]
    2: place too much a load on; "don't overload the car" [syn:
       overload, surcharge, overcharge]

Moby Thesaurus II by Grady Ward, 1.0:

124 Moby Thesaurus words for "overcharge":
   adorn, aggrandize, amplify, anticathexis, ballyhoo, bleed,
   bleed white, build up, burlesque, caricature, carry too far,
   cathectic energy, cathexis, charge, choke, clip, color, congest,
   congestion, convolute, countercathexis, cram, crowd, decorate,
   desire concentration, draw the longbow, drench, elaborate,
   embellish, embroider, energy charge, engorgement, enrich,
   exaggerate, exploit, exploitation, extortion, festoon, fleece,
   flourish, fudge, gild, glut, gluttonize, go to extremes, gorge,
   gouge, highway robbery, hold up, holdup, hyperbolize,
   hypercathexis, hyperemia, involve, jam, jam-pack, lay it on,
   load with ornament, loan-sharking, magnify, make much of, ornament,
   overassessment, overbrimming, overburden, overdo, overdraw,
   overestimate, overfeed, overfill, overflow, overfreight,
   overfullness, overlade, overlay, overload, overpaint, overpraise,
   overprice, overreach, overreact, oversell, overspeak, overspill,
   overstate, overstress, overstuff, overtax, overweigh, overweight,
   pack, pad, pile it on, plethora, profiteer, puff, repletion,
   satiate, satiety, saturate, saturation, screw, shylocking, skin,
   soak, stick, sting, stretch, stretch the truth, stuff, supercharge,
   supersaturate, supersaturation, surcharge, surfeit, swindle,
   talk big, talk in superlatives, tout, travesty, trick out, usury,
   varnish, victimize