The Collaborative International Dictionary of English v.0.48:

Shapeless \Shape"less\, a.
   Destitute of shape or regular form; wanting symmetry of
   dimensions; misshapen; -- opposed to shapely. --
   Shape"less*ness, n.
   [1913 Webster]

         The shapeless rock, or hanging precipice. --Pope.
   [1913 Webster]

WordNet (r) 3.0 (2006):

shapeless
    adj 1: having no definite form or distinct shape; "amorphous
           clouds of insects"; "an aggregate of formless particles";
           "a shapeless mass of protoplasm" [syn: amorphous,
           formless, shapeless]
    2: lacking symmetry or attractive form; "a shapeless hat on his
       head"

Moby Thesaurus II by Grady Ward, 1.0:

206 Moby Thesaurus words for "shapeless":
   aberrant, abnormal, adrift, afloat, aimless, aleatoric, aleatory,
   alternating, amorphic, amorphous, anarchic, anomalistic, anomalous,
   baggy, battered, bent, blind, blobby, blurred, blurry, broad,
   cacogenic, capricious, casual, chance, chancy, changeable,
   changeful, chaotic, characterless, clear as mud, cloudy, confused,
   dark, deformed, desultory, deviable, deviative, different, dim,
   disarticulated, discontinuous, disjunct, disordered, disorderly,
   dispersed, disproportionate, distorted, divergent, dizzy,
   eccentric, erratic, fast and loose, featureless, fickle, fitful,
   flickering, flighty, flitting, fluctuating, foggy, formless,
   freakish, frivolous, fuzzy, gargoylish, general, giddy, gratuitous,
   grotesque, haphazard, hazy, heteroclite, heteromorphic,
   hit-or-miss, ill-defined, ill-made, ill-proportioned, ill-shaped,
   immethodical, impetuous, imprecise, impulsive, inaccurate,
   inchoate, incoherent, inconsistent, inconstant, indecisive,
   indefinable, indefinite, indeterminable, indeterminate,
   indiscriminate, indistinct, inexact, infirm, inform, irregular,
   irresolute, irresponsible, kaleidoscopic, lax, loose, lumpen,
   malformed, mazy, meaningless, mercurial, misbegotten,
   misproportioned, misshapen, misty, monstrous, moody, muddy, murky,
   nebulous, nondescript, nonspecific, nonsymmetrical, nonsystematic,
   nonuniform, obscure, opaque, orderless, planless, promiscuous,
   rambling, random, restless, roving, scatterbrained, senseless,
   shadowed forth, shadowy, shifting, shifty, shuffling, spasmodic,
   spineless, sporadic, stochastic, straggling, straggly, stray,
   straying, subnormal, sweeping, systemless, teratic, transcendent,
   twisted, unaccountable, unarranged, uncertain, unclassified,
   unclear, uncontrolled, undefined, undependable, undestined,
   undetermined, undirected, undisciplined, unfixed, unformed,
   ungraded, unjoined, unmethodical, unnatural, unordered,
   unorganized, unplain, unpredictable, unreliable, unrestrained,
   unsettled, unshaped, unshapely, unsorted, unspecified, unstable,
   unstable as water, unstaid, unsteadfast, unsteady, unsymmetrical,
   unsystematic, ununiform, vacillating, vagrant, vague, variable,
   veiled, vicissitudinary, vicissitudinous, volatile, wandering,
   wanton, wavering, wavery, wavy, wayward, whimsical, wishy-washy