The Collaborative International Dictionary of English v.0.48:

Monstrosity \Mon*stros"i*ty\ (m[o^]n*str[o^]s"[i^]*t[y^]), n.;
   pl. Monstrosities (m[o^]n*str[o^]s"[i^]*t[i^]z). [Cf. F.
   monstruosit['e]. See Monstrous.]
   The state of being monstrous, or out of the common order of
   nature; that which is monstrous; a monster. --South.
   [1913 Webster]

         A monstrosity never changes the name or affects the
         immutability of a species.               --Adanson
                                                  (Trans.).
   [1913 Webster]

WordNet (r) 3.0 (2006):

monstrosity
    n 1: a person or animal that is markedly unusual or deformed
         [syn: freak, monster, monstrosity, lusus naturae]
    2: something hideous or frightful; "they regarded the atom bomb
       as a monstrosity"

Moby Thesaurus II by Grady Ward, 1.0:

111 Moby Thesaurus words for "monstrosity":
   aberrance, aberrancy, aberration, abnormality, abnormity, abortion,
   absurdity, amorphism, anomalism, anomalousness, anomaly, anticness,
   awfulness, baboon, bag, barbarity, bizarreness, bizarrerie,
   blemish, blot, bowlegs, camelback, cleft palate, clubfoot,
   crookback, curiousness, defacement, deformation, deformity,
   derangement, deviation, difference, disfigurement, divergence, dog,
   dreadfulness, eccentricity, enormity, enormousness, erraticism,
   eyesore, fantasticality, fiendishness, flatfoot, freak,
   freak of nature, freakishness, fright, frightfulness, gargoyle,
   ghoulishness, grotesqueness, grotesquerie, hag, harelip, harridan,
   heinousness, hellishness, heteromorphism, hideousness,
   horribleness, horridness, horror, hugeness, humpback, hunchback,
   immensity, inferiority, irregularity, knock-knee, kyphosis,
   lordosis, malconformation, malformation, mess, miscreation,
   misproportion, misshape, monster, monstrousness, mutilation,
   no beauty, oddity, outlandishness, peculiarity, prodigiousness,
   quaintness, queerness, scarecrow, sight, singularity, splayfoot,
   strangeness, stupendousness, subnormality, superiority, swayback,
   talipes, teratism, teratology, torticollis, tremendousness,
   truncation, ugly duckling, unnaturalism, unnaturalness, valgus,
   vastness, weirdness, witch, wryneck



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

monstrosity


    1. n. A ridiculously elephantine program or system, esp. one that is
    buggy or only marginally functional.

    2. adj. The quality of being monstrous (see the section called
    ?Overgeneralization? in the discussion of jargonification). See also 
    baroque.