The Collaborative International Dictionary of English v.0.48:

Distortion \Dis*tor"tion\, n. [L. distortio: cf. F. distortion.]
   1. The act of distorting, or twisting out of natural or
      regular shape; a twisting or writhing motion; as, the
      distortions of the face or body.
      [1913 Webster]

   2. A wresting from the true meaning. --Bp. Wren.
      [1913 Webster]

   3. The state of being distorted, or twisted out of shape or
      out of true position; crookedness; perversion.
      [1913 Webster]

   4. (Med.) An unnatural deviation of shape or position of any
      part of the body producing visible deformity.
      [1913 Webster]

WordNet (r) 3.0 (2006):

distortion
    n 1: a change for the worse [syn: distortion, deformation]
    2: a shape resulting from distortion [syn: distorted shape,
       distortion]
    3: an optical phenomenon resulting from the failure of a lens or
       mirror to produce a good image [syn: aberration,
       distortion, optical aberration]
    4: a change (usually undesired) in the waveform of an acoustic
       or analog electrical signal; the difference between two
       measurements of a signal (as between the input and output
       signal); "heavy metal guitar players use vacuum tube
       amplifiers to produce extreme distortion"
    5: the act of distorting something so it seems to mean something
       it was not intended to mean [syn: distortion,
       overrefinement, straining, torture, twisting]
    6: the mistake of misrepresenting the facts

Moby Thesaurus II by Grady Ward, 1.0:

215 Moby Thesaurus words for "distortion":
   aberrancy, aberration, abstractionism, abuse of terms,
   anamorphosis, apparent soundness, bad likeness, birdies, birthmark,
   blackhead, bleb, blemish, blister, blooping, blurping, botch,
   bulla, burlesque, caricature, casuistry, catachresis, check,
   cicatrix, circularity, coloring, comedo, confabulation, contorting,
   crack, crater, craze, daub, defacement, defect, defectiveness,
   deflection, deflexure, deformation, deformity, delusion, deviancy,
   diffraction, diffusion, disfiguration, disfigurement,
   disingenuousness, dispersion, eisegesis, equivocalness,
   equivocation, errancy, erroneousness, error, evasive reasoning,
   exaggeration, expressionism, fallaciousness, fallacy,
   false coloring, false swearing, falseness, falsification,
   falsifying, falsity, fault, faultiness, feedback, flaw, flawedness,
   flection, flexure, flutter, fluttering, freckle, garbling, gloss,
   hamartia, hemangioma, heresy, heterodoxy, hickey, hissing, howling,
   hum, hyperbole, illusion, inaccuracy, injustice, insincerity,
   jesuitism, jesuitry, keloid, kink, lentigo, litotes,
   malconformation, malentendu, malformation, malobservation, milium,
   misapplication, misapprehension, miscitation, miscoloring,
   misconception, misconstruction, misdoing, misdrawing,
   misexplanation, misexplication, misexposition, misfeasance,
   misintelligence, misinterpretation, misjudgment, mispainting,
   misquotation, misreading, misrendering, misreport,
   misrepresentation, misshape, misstatement, misteaching,
   mistranslation, misunderstanding, misuse of words, mole,
   motorboating, mystification, needle scar, nevus, nonrealism,
   obfuscation, obscurantism, overdrawing, overstatement,
   oversubtlety, parody, peccancy, perjury, perversion, philosophism,
   pimple, pit, plausibility, plausibleness, pock, pockmark,
   port-wine mark, port-wine stain, prevarication, pustule,
   rationalization, refraction, rift, rumble, scab, scar, scatter,
   scratch, scratching, scribble, sebaceous cyst, self-contradiction,
   shredding, sin, sinfulness, skewness, slanting, sophism,
   sophistical reasoning, sophistication, sophistry, special pleading,
   speciosity, specious reasoning, speciousness, split, squeals,
   squeezing, static, straining, strawberry mark, sty, subtlety,
   torsion, torturing, track, travesty, twist, twisting,
   understatement, unorthodoxy, untrueness, untruth, untruthfulness,
   verruca, vesicle, vicious circle, vicious reasoning, wale, warp,
   wart, weal, welt, wen, whistles, whitehead, woomping, wow, wowwows,
   wrenching, wrong, wrongness